Ya, a lot of people are hella ghey at concerts. Even if they like the band, they will throw stuff at them. I recently went to the Static-X concert and people threw stuff. Nothing like rocks or anything to hurt the band, just like bottles and shoes and stuff. Its hella bull shit. The band always says to beat some ass if somebody throws something, but nobody ever gets hurt.
Dude, hella people throw shit. If I was a big buff guy (I'm only 6'1" 185lbs) that could kick some ass, and I saw somebody throw something at one of my favorite band, I would for sure punch them in the face.