Occasionally a mill does get shut down, like the one in North Texas, and then local animal agencies and nonprofits, who are already stretched and underfunded, have to pick up the pieces and help the poor animals who have been living in the terrible, abusive conditions.
In addition to supporting a cruel business, when you buy a puppy from a pet store, you will likely pay a lot of money for a puppy who is unsocialized, sick from poor vet care, and has genetic problems due to overbreeding.
While we at APA! hope that everyone will adopt a shelter pet, if you decide to instead buy, please follow these guidelines from the Humane Society to find a responsible breeder and avoid buying a puppy mill dog.