I remember seeing a 'cabaret' hypnotist working a private party -- one of the tricks was the one Mark mentioned above, making a very tall guy (a policeman as it happened) lie rigid face up between two chairs with people sitting along his body. The thing is, while he was hypnotising his subjects, a woman in the crowd appeared to go under the influence as well. I brought this to his attention and he brought her out of the trance and stressed that it would be very dangerous for a member of the audience to go away in that state. As I said, this was a private party and neither the policeman or the woman in the crowd could have been stooges. Maybe something like that happened to Guest 3.26.
I also worked with Paul McKenna when he was a DJ and just starting out as a hypnotist, and saw his stage show several times. As Gerald suggested above, this would involve whittling a large crowd of volunteers down to a few very susceptible subjects. He tried to hypnotise me once, but I didn't go under, even though I really wanted to try it!

BJ