I don't think that people who at concerts are assholes. It's not distracting to anyone else, especially since most people usually have cameras and/or are using their cells as cameras there.

One of my best friends texts during movies ALL the time though and she doesn't even try to be discreet about it. She literally holds her phone up in front of her and texts away like she's playing a video game. It annoys the hell out of me and I'm sure almost everyone else in the theater behind us too. I've said things to her about it before, but she still does it.