I don't think I've ever been to any concert (FM/SN or otherwise) and not had a run-in with drunks.
The only notable one was at one of Stevie's 2005 shows; a guy behind me had his daughter (5, 6 yrs old?) sitting on his shoulders for most of the show and her feet were constantly kicking the back of my shoulders. He was screaming at the top of his lungs and encouraging her to do the same, which I'm typically fine with as I'm not exactly quiet at concerts either. I tried putting up with the kicking since she was a child, but finally shot a dirty look over my shoulder in his direction. Of course this set him off and he had a stream of insults and comments to make for the latter half of the show. I would have responded but tried to be the bigger person for the sake of his kid.
When it came time for the Edge walk, he put her down with his wife/girlfriend and tried to stagger to the stage. I tripped him, stepped over his head and proceeded to get my first handshake from Stevie!
