Keep in mind that these answers are based on what I have researched and found personally to be true.  I am not a Vet or an expert.  I am a small breeder who has had some small experiences, learned a bit, and am willing to share my beliefs.
Hopefully there is something here that will help others.

Gender does not directly determine intelligence, affection, sociability, submission, dominance, aggression, activity level, ability to be housetrained, willingness to learn or much else in a dog.

Just like with people each dog has a different and distinctive personality.  That is why we take the care we do in placing a puppy or dog in a new home.  It is important for the personalities of the dog and their new people be a compliment.

Pomeranians primarily shed their undercoat, which requires brushing all the way to their skin during that shed or matting will occur. A Pomeranian does not require as much grooming as some of the other long haired breeds (or even some short coated breeds). Be prepared to brush your dog two or three times weekly. Grooming should be a time enjoyed both by your Pomeranian and yourself.

Each dog is an individual and has different learning curves and responds to different methods of training differently. High intelligence doesn't always make a dog more trainable, sometimes it just makes them more wily in ways to thwart you! HUMAN BONDING is the single most important factor in your dog's trainability. You must be bonded to your dog for it to even want to please you. Can you blame it? I don't have much desire to please a stranger, or someone I don't like myself, so I can't blame the dogs too much.

Age also plays a role in in how well they house train.  Puppies will have to go to the bathroom more often than an adult.  There are many aids and methods in potty training. 

Absolutely you should alter your pet.

One of the leading causes of death in pet animals is mammary gland and testicular cancers. Early altering will prevent the sexual maturation and greatly reduce (almost eliminate) the incidence of these cancers.

One of the most common reasons animals are abandoned have to do with housebreaking. The scent of estrus is noticeable to dogs for five miles! Instinct causes your dog to respond to this scent with urinating in their surroundings to mark their territory. Females piddle in tiny amounts and therefore it is less noticeable, and males lift their leg and urinate on objects to mark territory-which is more noticeable, but both genders mark their territory when left unaltered. Since the scent of urine is present-it then causes problems with defecation in the house as well. Since sexual maturity occurs in toy breed dogs well before the age of one year old this makes it advisable to alter your pet between the age of five and seven months of age (In boys, before they learn to lift their legs). Most vets recommend this age as well.

Two very good reasons to alter your pet.

The activity level and diet of your pet determine it's weight.  If unusual weight gain happens then thyroid testing may be in order, or outside sources of food not under your control, well meaning neighbors for instance, should be considered.  Maybe they just need to start going for a long evening walk.

There are good reasons to breed an animal that is not major faulted, but this certainly isn't one of them! You are jeopardizing the future health of your pet by doing so. (See the section on "Should I spay/neuter?") Breeding will not "settle down" an animal with a behavior problem.  As soon as the dog's energy returns, after the ordeal of the whelping (in a female) and within 1 hour of the mating (in a male), their youthful exuberance will return to their normal "un-settled" state.  Then you will also have a young dog who is not a pet anymore, but a breeding animal with all the accompanying instincts and a whole new set of problems.

For behavior problems you should seek professional assistance from someone who is experience in training.  

Many litters each year are bred for the wrong reasons.  They end up in all kinds of situations.  If they aren't surrendered or euthanized they end up in over crowded situations with owners that really just wanted to "settle down" the parent and were not prepared for the stress and expense of a whole litter of puppies that are not settled...  You'll sacrifice way more than you'll ever gain from that litter.

If you do breed for the right reason, to carry on a wonderful lineage from a wonderful example of the breed, be prepared to deal with the many problems that surface after the arrival of the litter. Ask yourself some questions. 

•  Can you take off work for at least the first four weeks to ensure the survival of the litter when the mother does not survive whelping?  These puppies will have to be bottle fed every two hours for those four weeks.
• Do you have firm buyers-and deposits for all the possible puppies, and will they make good homes for the dogs? (Hint-make sure they have references.)
• Are you now prepared to deal with the probable behavior changes your dog will develop due to mating instincts in the future?
• Since behavior is a genetic trait that will be inherited by the puppies.  Are you now prepared to deal with that behavior problem you have passed to those puppies, in your attempt to "settle it down"?

It is bloody, agonizing, and potentially very dangerous to the dog and the puppies. MANY small breed females have Caesarean sections and MANY of them die. That is not something I would wish to subject my young children to. Children are usually very emotionally involved with their pet and it is a potentially traumatic experience for them, far from the "miracle" you hoped it would be.  Additionally you are putting the life of their much loved pet at risk with any pregnancy. What kind of "miracle" would that child see to watch their pet and her puppies die during that "miracle"?

Between baths you can use a bit of baby powder for a dry cleaning that keeps them sweet smelling. Make sure not to get the powder in the Pom's nose.  You can also use a "steam bath" method of taking a VERY hot wet towel and wrapping it around the dog for a few minutes, then rub vigorously. The steam bath will remove a great deal of soil from their coat.

Brush with a metal pin brush (the longer pins the better) and metal detangling comb thoroughly at least once per week.  I keep my brush on my coffee table and brush someone every evening while watching television.  Watch for mats behind the ears, under the front arms and along the backs of the legs as these are the areas where the coat is finer and will tend to mat.  Be sure to brush before a bath and after the coat has dried after a bath, that is when you will get most of the loose coat out.

Expect a blow again at the one year shed.  Males will achieve their full and glorious coat at about 2 years of age.  The Female, on the other hand, is another story.  Expect her coat to blow with each season and each litter and take about 6 months to re-coat.

Puppy Mill - A breeder who produces puppies hand over fist with no breeding program, little attention to puppy placement , and poor health and socialization practices.  A puppy mill may or may not be dirty, but is usually overcrowded.  Dogs may be neglected because the breeder can't properly handle as many dogs as they have.  Puppy mills are not conscious of breeding genetic issues or breeding with the AKC standard in mind.

Backyard Breeder - A dog owner whose pet either gets bred by accident or who breeds on purpose for a variety of reasons.  This breeder is usually ignorant of the breed standard, genetics, behavior, and good health practices.  This is often the breeder who is breeding a couple of dogs just to make a bit of extra cash. 

Commercial Breeder - One who usually has several breeds of dogs with profit as the primary motive for existence.  the dogs may be healthy or not and the kennel may be clean or not.  The dogs are probably not screened for genetic diseases and the breeding stock is probably not selected for closeness to the breed standard or for good temperament.  Most commercial breeders sell their puppies to pet store or to brokers who sell to pet stores.

Show Breeders - A breed fancier who usually only has one breed, but may have more.  They follow a breeding plan in the efforts to preserve and protect the breed.  A show breeder will keep their numbers small so that all have the personal attention they disserve.  They produce a small number of litter per year, breeds only when a litter will enhance the breed and the breeding program.  They raise the puppies with plenty of environmental and human contact.  They have a contract and health guarantee that protects the breeder, dog and the buyer.  They run a small clean kennel; screen breeding stock to eliminate hereditary defects from the breed; works with a  breed club or kennel club to promote and protect the breed; and cares that each and every puppy is placed in the best home possible.  A show breeder will usually be active in some type of rescue program.

Ok, so now to answer the question...

The first most obvious reason is the overall quality of the animals they produce. Because of ignorance (or disregard) in how to breed quality, puppy mill & backyard breeder puppies are often genetically defective and will cost you much money, time & heartache to prolong their life. If you're lucky you won't invest hundreds or thousands of dollars at your vet's for that $200 puppy.

In buying from a show breeder you are getting a puppy where the best qualities have been considered in the breeding program.  You will gain a person who is willing to support you with their expertise and advice in your ownership of your Pom. A show breeder will offer resources, such as booklets and websites, with helpful answers to your most asked questions.  They will be available by telephone or e-mail for helpful advice regarding your puppy. In using a respected show breeder you can expect a positive experience regarding your dog's ownership from them.

"Bargain " dogs don't usually end up being much of a bargain.

ALL pet puppies of either gender have limited registration and no puppies from them can ever be registered with the AKC. If you purchased a pet puppy from me you also signed a contract that you would have that pet altered. 

If you purchased a breeding quality female, then the answer is yes, but please read the cautionary statements above first and decide if you really want to be a breeder.  For instance:  Do you know how to tubefeed a weak puppy?  Are you financially prepared to give your breeding females the care they may need when they have problems with a pregnancy? Are you committed to becoming a breeder and have the betterment of the breed in mind with your program?

If you are committed to becoming a show breeder and are prepared for the risks involved, I will help you succeed to the best of my ability. Even dog breeders like company in this often heartbreaking profession and often we need a spare shoulder to cry on, or someone to share a triumph with. If you like roller coasters you might like breeding.

If the breeder who is doing the line/in breeding understands what they are doing, and has done the proper genetic investigation, line and in breeding can be a great benefit to a breeding program.  It can allow a breeder to strengthen a desired trait within a line.  It has to be done carefully and may include genetic testing and extensive line research.  Not only can line/in breeding strengthen a desired trait and be used to eliminate faults.  It can also bring out other hidden faults.  Doubling up on a line that carries heart disease or collapsing trachea is going to strengthen those traits as well as the good trait you were originally looking for.

As you can see if the breeder is a backyard breeder who doesn't really understand what they are doing, are guessing, and are not doing the proper genetic investigation it can produce disastrous results.  This is just one more reason to find a reputable show breeder for your puppy.

Toy breeds,in general and not exclusively, are prone to those problems.  The speed that the Pomeranian breed has come down in size has contributed to the issues that are seen with most breeds of dogs.  A reputable show breeder is doing careful genetic selection and is not breeding animals that have or produce those issues, so no, not all Poms have the problems.  Visit with your breeder, talk to them about the kind of breeding problem they have, watch the parents of the dog you are purchasing.  If the parent has a problem, then it is likely the puppy will also have it. 

OK, first the disclaimer...  I am not a Vet what I say here is my own personal opinion...  Now for the opinion... 

We have also seen an alarming trend for un-necessary expensive surgeries (especially in the area of knee issues).  If your Vet is telling you that your dog needs knee surgery we recommend a couple of things to try before jumping into that traumatic event. 

• See an Animal Chiropractor.  They should be board certified.  They are finding that often times something out in the back can give the appearance of being a knee issue where it is truly just a symptom of the real problem.  If it is a problem with spine alignment you should see results very quickly. 
• Put your dog on Gluclosamine.  If you see results from this (and you should within the first couple of weeks of starting), it could be that this isn't an issue requiring surgery, but an injury that needs time and physical therapy to resolve (time to get a second or third opinion).
• Create your own physical therapy program.  Think of the things that a therapist will do to exercise the joint of a human.  Visit with your Vet about the types of movement that a dog's muscles require.
• Lastly get a second and third opinion, not just from specialists, but from the small rural vet as well.  Their recommendation should be basing this in fact, look at the ex-rays, take them with you to the other Vet's and have them look at them.  Make sure that they are looking at more than just the knees, but the back and hips as well. 

Then make your decision based on the knowledge that this isn't a quick fix.  You will be starting on a long path to recovery as not only will your dog be recovering from the surgery, you will be doing the physical therapy as well.  One additional piece of advice... knee surgery shouldn't cost $1000's of dollars.  Depending on your area it should be less than $1000 per knee.  Shop around, find someone you like and trust.

• American Pomeranian Club (APC) information on a research grant and several great articles about it
• Canine Genetic Disease Network
• AKC Canine Health Foundation
• Alaskan Malamute Health
• Case study and inheritance information
• Digest of a case by Pomrama

I am not sure this is true but this is what I have been told....................