There is no definitive answer to this question as opinions will vary from individual to individual. Some people believe that puppy mills are a common occurrence in the United States, and that this is because of the high demand for pet dogs. Others believe that puppy mills are not as common as they are made out to be, and that the puppies that are sold at pet stores and online are actually healthy and well-bred dogs. Ultimately, the answer to this question is likely a little bit of both.