Humane Society says: If you buy a dog from a pet store you are contributing to the most horrific kind of animal abuse.
The famous pet store chains buy their puppies from "puppy mills". In puppy mills, the puppies are forcefully bred which makes them very sick. They are kept in cages for the rest of their lives until they are bought, and they are separated from their mothers once they are born.
CBS News shows a clip.
So people, if you want to have a pet, don't buy from a pet store. Buy from an animal shelter or a neighbour.