I was at the Edinburgh Fringe Festival this week and I saw a few times when the audience members get a bit 'Excited'.
How it was handled by the professional street performers was this: They let it go. They just carried on with the show until that person walked off.
After they had walked off, my favourite response was "well we didn't need the %@!&£* anyway, did we guys!?!"
The audience seeing what an annoying person the volunteer was quite happily agreed and the show continued as normal.
My good friend that was doing the Fringe was doing a Straight Jacket Escape, and really wound up the guy that was strapping him into it. the guy knotted the straps after strapping them up. Although it took him longer to get out, he still did it and after explaining to the audience got a load of money right at the end.
There are lots of different ways to handle an audience and you just have to work out the best way for you.
Simon_Magic