When I got my Chinese hamster from Pets at Home I was not asked one question, even though there was a sign on Princess' tank that she was separated from her siblings due to fighting, THEN she was brought back by someone because they thought she was 'too shy and aggressive'.
So they weren't even interested in whether I was prepared for a possibly problematic animal. Though this was the last time I ever bought a hamster from a pet shop. She seemed to have been traumatized by her previous owner.
I don't think animals should be sold in shops at all. It'd be better for everyone if all pets for sale were removed from the high street, and their breeding and sale restricted to private specialist breeders only. I think it would save a lot of heartache for potential owners and it would save more animals from possible cruelty and mistreatment.
Just recently my boyfriend's sister has got a teacup chihuahua from a pet shop, only to have the RSPCA turn up at her door a week later seizing the poor dog, saying he's been illegally imported from Slovakia and they have no idea whether he received the necessary vaccinations. So his sister was worrying herself sick whether they all managed to contract rabies from this dog, and if he had turned out to have rabies, he would have been put to sleep. He spent 4 weeks in quarantine, thankfully he was all right. Guess what though, the pet shop owner went back to the quarantine [as there were people who didn't want the dogs after all the carry on] and got back two of his puppies [as all the dogs from that pet shop were seized] and is selling them...he's not been fined/arrested/charged and he was allowed to keep his pet shop open.
When I was at the vets a while ago with Princess, an old lady came up to me, looked at her and said 'why are you spending money on a dirty rat?' I was like erm, first of all, it's not a rat, it's a hamster and it's none of your effing business what I spend my money on.