Unfortunately, this sort of self-entitled behavior is a little too common and is often fueled by alcohol. I've gotten a few bruises from these people, but,for the most part, the "crew" of U2 fans tend to look out for each other. Seriously, U2 fans can be some of the coolest people!
I've got one really bad story though. One time this drunk guy kept on trying to push his way to the front for well over ten minutes. This caused aslight wave of fans accidently pushing each other forward. Sadly, the lady in front of me thought I was trying to steal her spot because instead of squishingher with my body (i.e. possibly injuring her!) I decided to brace myself by putting my hand on the rail. I tried so hard to explain to her what was reallyhappening, but she couldn't hear me (well, duh, we're at a concert and she was also drunk out of her mind) and so she ended up elbowing me severaltimes and pounding on my hand and yelling at me with some not-so-nice words! Gee whiz, at least I can laugh about it now. ;-)
Oh, besides enjoying the concert that night (with exception to the pushing, pounding, and elbowing), I also found $50 bucks on my way back to the hotel,which was quite a lot for a cash strap college student - I felt like a lotto winner after that. ;-)