Besides physical problems arising from breeding, there are other drawbacks for dogs' welfare. People make all kinds of demands on dogs, and keep them from exhibiting their natural behavior. For instance:
  • eating
  • walking
  • exercise
  • attention
  • social behavior
  • sexual behavior

Eating
The dog owner decides when, how much, how often and what kind of food the dog gets.

Walking
The dog owner decides where, how often and how long a dog is walked. It's walked at times that are convenient for its master. Often the dog has to be kept on a leash, limiting its freedom of movement.

Exercise
It often happens that dogs have not enough room to move around freely in the house. There's furniture and obstacles everywhere, and the room itself is just small. Dogs by nature are used to run and play a lot.

Attention
Dogs only receive attention when it's convenient for their masters. Of course, there's interaction between dogs and their owners, but if the owner doesn't feel like it, the dog gets no attention.

Social behavior
Dogs are social animals. They are used to having their own place within the pack. When dogs are accepted into a family home, they should be awarded the lowest social rank. Not all dogs will accept this easily, which can cause conflicts that may get out of hand (especially with children).
Contact with other members of their species is often limited. By nature, dogs are pack animals, they live in groups with other dogs. People often have just one dog, and it cannot exhibit its natural behavior with members of its species. The dog's natural behavior doesn't concur with what its owner wants, and its conditioned behavior is unnatural.

Links inside Animal Freedom:

Bad arguments for keeping pets

Aspects
Pets
An example: the dog
The history of dogs
Modern day dogs
Consequences of irresponsible breeding for dogs
Drawbacks for dogs
Pets
The pet-industry
Man
Why do people want pets?
Drawbacks for humans
Conclusion?
Take a pet?

Sexual behavior
Suppressing sexual behavior is part of a dog's training, because this natural behavior is something we do not like. Think about dogs "humping" legs, excitement and chasing other dogs.
Castration and sterilization are common, to make sure no unplanned litter is born. Another reason is to suppress sexual drive, which is often seen as an undesirable characteristic.

Of course there's interaction between dogs and people, but this is mostly one-sided. People own dogs, are the leaders and make the decisions. Although there are plenty of people who want nothing but the best for their dogs, this doesn't change the fact that in the end people impose their wills on dogs. Dogs are restricted in almost every natural behavior and need, and have to yield to people's "needs".

In their natural surroundings, dogs are also limited by their place in the pack's social rank. But with humans these restrictions are more extreme. In nature, dogs will not always have the lowest rank, such as they do with people. They are not kept on a leash, restricting their movements, they can answer nature's call when necessary and they have much more social interaction with members of their species.

By taking dogs as an example, we have touched upon various factors that normally you don't think about much. Not all, but most of these arguments also apply to other pets. On the other hand, there are also factors that apply to other kinds of pets and not to dogs. There are more consequences for pets.