First off, hynotism is very real. It's not magic, it's not completely controlling somebody, it's putting somebody in a trance-like state then offering suggestion.
When you're in this trance-like state, all your faculties are working... hearing, seeing, feeling, speaking, etc, except one, which is your critical reasoning (which some people don't even use when they're fully conscious). So if the hypnotist suggests to you to perform something in this state, and as long as it's not against your internal moral beliefs, then you'll do it. If he says that your watch is really 50lbs, you're going to really think your watch is 50lbs and you're going to have a hard time carrying it.
Don't underestimate the power of suggestion. Even when fully conscious, we're quite subject to the power of suggestion. I remembered when i was younger, somebody told me a version of an accident that was false (i had a different memory of it)... at the time i knew he was wrong, but as the more often he told it, eventually i CAME to believe it was absolutely true. It was only years later that he admitted the lie and i remember the true events, but according to my memories all those years, it was his fabrication of it.
Anyways, almost everybody can be hypnotize... if they're willing. If you go on stage believing you won't, or don't want to, then there's nothing the hynotist can do to you to make you relax enough to go into a trance like state.
I suggest going to a live show and see if it's real. Sometimes, you will see the odd person that can't be hypnotize, mostly because they're so nervous or unwilling to get into a relax state. But most of these shows try to get a large number of the audience involved, so most likely you'll know somebody who's being pulled onto the stage... and i'll bet they weren't paid to pluck around like a chicken.