One of my biggest pet peeves is people using their phones to film live concerts. I mean, what do you intend to do with that thing anyway?
Upload it on YouTube. Duh! And who's gonna sit through two hours of unbearable low quality audio and video when yours is only one out of thousand similar videos and the official live DVD is probably coming out w/in a year? In the meantime, you're ruining MY experience...
I know most probably can't even answer the first question. They've seen others do it, that's why they do it.
It irks me even more when an announcement is made at the beginning of the show that filming is not authorized. And the minute the lights go down, you see all those tiny phone screens in the air...