I bought Zahra from a pet store. Okay, beat me up, I know that I should not have but my heart broke when I saw her the first time in the pet store and then over a month later saw that she was still there. No one seemed interested in her.
I knew all about puppy mills, I always said we would buy from a breeder, adopt from a shelter, etc.
We have been lucky with Zahra, she has only so far had Mange and behavior wise potty training her has been tough. Do I wish I would not have bought her? No. Do I wish I would have adopted her or got her from a breeder? YES, then I would not feel guilty about supporting puppy mills and about the Basenji breed being compromised by bad offspring for profit.
I had only had cats previously and had always adopted from the Humane Society, Animal Shelters, SPCA, etc. My last cat was adopted through a rescue that was at PetSmart, after 10 months and a lot of vet bills my cat was diagnosed with Leukemia and had to be put to sleep even though the rescue claimed to have done all the test (long story but it turns out that the rescue may not have been very reputable).
I too had always wondered, with the gut wrenching thought of what probably happens to pet store animals that are not adopted.