i've been to shows where people have been able to sneak in cameras to the venue. however, they did the dumb thing and left their flash on!
obviously, if you take several pictures in a row using your flash, that is a giant beacon to any security who are in the area. and sure enough, i have been near one or two bright people who have left their flash on and then had security up in their face about it.
you know...like all those people who go to the superbowl and start snapping away.
however, need i remind people that flashes are only good up until a certain distance? unless you are very close to the stage, you might as well forget about it because all you're doing is lighting up the back of the head of the guy in front of you and making moz seem more like a dark speck in the distance. these people would have done so much better had they just left their flash off because they could have snapped away because security has other things to worry about than going on camera patrol.