To shed a slightly different light on this. Some comments refered to other people filming the show. I'm one of those people that upload, I would like say decent video's from concerts, including U2, on Youtube. I started out about 7 years ago around the time of the first 360 shows. I wanted to have decent video's of the concert that I went to, so I could enjoy it again. But as most concert vids on Youtube are crap and the official dvd is good, but usually a pimped videoclip style video from a show that I did not attend, I decided to try it myself.
I take notice of the people around me when I'm at the show. I don't want to be in the way too much of anyone. I don't use a phone but a compact camera, which I set to a low brightness level. A steady hand, proper framing and solid audio makes for a good concert video. I've had many people enjoy and comment on my uploads which is gratifying. I don't always film everything or sometimes nothing at all. I often go to multiple shows, so I think it's worth it for me.
But as others have said, if its just to have some facebook pics or to show people the next day, just take a few snap/selfies and a clip and then put it away. Basically, go all the way, or just keep it at that. Also, a camera on your head is cool with sports, but you head moves a lot. And a shaky vid is very hard to watch. Also, if you have the bad luck to be behind a tall guy, then you are done anyway.