I'd challenge any "hypnotist" to make me do anything, even something simple like standing up from a chair. Guess what's going to happen: I'm going to remain sitting, and likely become bored.I saw a hypnotist at a comedy club and am absolutely certain it is a real phenomenon. A good hypnotist can make you do anything (at least short term)..
I know the ads you're talking about. He certainly has no shortage of testimonials from satisfied customers. I guess I would say that even if it doesn't work for everyone, it seems to work for many. Wanting it to work probably is a factor.
To the best of my knowledge, it hasn't yet been shown to have a significant effect after controlling for a client's/participant's desire to want to affect a change. Some of its components, such as the relaxation aspect, do indeed induce physiological changes, though (in much the same way that deep breathing, muscle relaxation, meditation, etc. do).

 
				
		