Like any animal from a pet store...it could be sick,diseased and unsocialized.
Very true, I learned that the hard way. Since I didn't know any better at the time, I bought two netherland dwarves from a Petland (yeah, don't need to tell me it's a mistake, I know now), and got them taken to the vet within a few days of getting them. Vet did a checkup, said they both seemed fine, nothing appeared to be wrong with them.
A week later, the first one of the two got diahrrea and ended up dying despite us rushing him to an emergency vet at 5 in the morning. Less than a week later, his twin sister from the same litter died of the same. The vet techs there said it happens all too commonly to rabbits that are weaned too soon. The breeders (rabbit versions of puppy mills) sell them too young to the pet stores, who then have NO idea what they're doing and just sell them off as soon as possible to maximize their profits.
That's not to say every pet store is necessarily bad, as we got another bunny around the exact same time from a different store, and she's been doing great. The difference is that they actually had an older gentleman working there who seemed to genuienly care for their animals, instead of acting like they're just products on a shelf.
So from personal experience, I would had to suggest going to a rescue shelter to see if you can't find a rabbit you'd like there. If that fails, contact your local House Rabbit Society chapter (rabbit.org) and see if they have any rabbits that are looking for a home. Or check on Craigslist/Hoobly/Kijiji and check the pet classifieds. Some breeders are probably fine, but there's plenty of them who are only one step better than pet stores, since they're the ones providing the pet stores with all the rabbits.
I know everyone always preaches about how you shouldn't get your pets from a pet store, but it's really only personal experience that will drive the point through. You could get lucky, but you could also end up with a sick pet that ends up dying and costing you hundreds of dollars in vet bills.
Edit: As an addendum, Jess does have some really good points there. Even without getting into the whole "it's the right thing to do"-factor, adopting a rabbit from a shelter will also make it easier for you. They'll probably be litter trained, almost certainly spayed/neutered, and they'll be somewhat used to human contact. The rabbits at a pet store are constantly in a loud environment with all sorts of children pulling and tugging at them from every direction. They'll probably be scared of you, won't ever have seen a litterbox, and you'll be looking to shell out a pretty penny in about 4-6 months to get them fixed. That's in addition to what I said above - your rabbit could just end up being sick and dying despite your best attempts.