I have had a few experiences like TheDisneyGirl's here in California. Luckily, it's only been maybe 4 occurences (I think it's because I just lace my voice with sweetness, and I've nailed the "no really, I am sorry" face after three years).
My first ever experience did bring me to tears though. We were closing the Winnie the Pooh location in Critter Country, and finishing up the line when a family tried to enter through the exit. My friend and I told them that the line was closed but Pooh and his friends would be walking around the area in about 15 minutes. The two mothers in the group went OFF. They were cursing and screaming at me (with their children right behind them), then one of them has the gall to grab her child's arm (who by the way was already crying), pull her forward and bark "Tell this nice lady THANK YOU for ruining you trip!" another person from the group went and got their strollers and the group finally left after yelling at us for about 10 minutes, cursing and yelling the whole way out of Critter Country.
As it turns out, they did go to City Hall to complain. THeir interaction with my manager went like this:
Manager: hello, how can I help you?
Irate Guests: Yeah we were just dealing with some (expletive) who was with Winnie the Pooh who said we couldn't visit with him until later.
M: Oh, do you remember her name?
IG: No
M: Do you remember what she looked like?
IG: No
M: Did you go back to visit the characters when she told you they'd be back?
IG: No
M: well I'm sorry, but I can't help you then *Turns around and walks out*
Ah, the joys of good parenting. It seems most of the really irate guests I get are in Critter Country, thankfully I haven't been there for a year