Generally if a store employee gets "snooty" with a customer, it's usually being returned to said customer who has been dishing it out ad nausium from the time they walked in the door. People forget respect is two way street and if you treat somebody like trash, don't be surprised if there aren't rose petals from them everytime you walk in the door.
BTW, Yoda (Noel) turned me on to this comic strip, had plenty of been there, done that's between my sister, mom, and myself between all of us working retail and my sister's library job too.
http://www.retailcomic.com/?p=3551