Not all Petco/Petsmarts do a bad job with their reptiles. Many times the people in charge of working those areas are reptile keepers and pay a good amount of attention to detail. I'm one of those morons who bought a perfectly healthy bp from a Petco a few years back. One of my girls really wanted him so he came home with us. He's always been a healthy snake with good appetite and is actually the favorite snake in my home.
While I think that there are many other avenues these days for buying a snake such as a solid private breeder, I don't think it's right to lump the entire chain together. My local Petco does a good job in their reptile dept. Hopefully many more of the morons such as myself have had positive experiences as well