From personal experience: they just take your camera - give you a receipt to pick it up after the show and you're off back inside.
You miss one song - but if you DO succeed, it makes it realy worthwhile!
If I can make it to this show, my camcorder is coming with me. I'm shoving it down my pants. They'll need to dig deep to find it if they search. If someone takes it from me, oh well but it's going with me.