It doesn't bother me about mice and rats in petstores as long as they are carried for properly and care is given to whom they are sold to etc.
I agree that local shelters should be check first for adoptee's for any animal, rodent etc.
I know someone who is very deep into birds, Parrots mainly. And according to her, purchasing them from petstores isn't good on any level. The birds that they have come from byb's and bird mills. She is also heavily involved in Parrot Rescue etc and she says that the conditions etc are no different than with puppies etc. And if someone wants a Parrot, they should first do their research, try to rescue first or find a rep. Parrot Breeder.