i also see lots of people taking photos with their phones now. that's not quite as annoying as holding it up for friends to hear, but it's close.
(sort of like the high school chicks at radiohead who called their parents and held the phone up for their folks to hear...)
They Might Be Giants got pissed when they heard someone on the phone, and actually asked the entire crowd to hold up their phones and make the ringer go off. That was silly.
Oh, and I was at some other show where the band took someone's cell phone. Then, a friend called it from in the crowd, and got to talk with the band. Damn, I forgot what show that was. But it was funny. (I need to stop drinking so much at shows.)