This article is from the Getting A Cat FAQ, posted to rec.pets.cats newsgroup. Maintained by Cindy Tittle Moore with numerous contributions by others.
Don't buy kittens from pet stores. Pet stores are notorious for selling unhealthy or poorly bred purebreds, and even irresponsibly bred non-purebreds. Kittens sold in pet stores are outrageously expensive, often two to four times more expensive than the same type of kitten bought from a private breeder. They are often obtained from "kitten mills," where animals are poorly treated and bred (and bred and bred) for profit. By buying from the store, you are supporting these mills and adding to the pet overpopulation problem.
Some stores claim that animals are all obtained from local breeders or "home raised." Employees are commonly instructed to tell customers that the kittens were obtained from local breeders, when in fact they were not. No responsible breeder would allow their kittens to be sold in a pet store, where they could not interview the buyer to make sure they are aware of the responsiblility of caring for an animal.
It is further suggested that you don't even patronize such stores. Take your business to stores that sell pet supplies only, no puppies or kittens.
One happy exception: Look for one of the increasing number of pet supply stores that work with the local shelter to help place the animals. These programs provide additional exposure and opportunities for the local shelter and are a wonderful example of constructive partnership for the benefit of our animals. However, make sure that the animals are being adopted out under the rules of the shelter involved.