Well I have been known to take photos at gigs, and do enjoy watching videos on YouTube, so call me a hypocrite, but......
I don't know why NMH did the "don't film or photo us" thing. It might have been that Jeff gets anxious (I would know how he feels, I get that anxiety with cameras and especially videos too- it can hit anyone!) or (more likely) it could be that they wanted to influence the sort of atmosphere they were playing in. If it's either of these, this should be their choice, as performers. They didn't "ban photography" as some have suggested, they just asked people not to photograph. There's a difference.
The key thing is, the moment people are taking photos, they're not fully listening and not fully watching. If you're watching on a screen, it feels a little bit like watching TV rather than having direct eye and ear contact. And these feelings are infectious. You lose a load of the intimacy of the show as a result. As it turned out, I think it was a really important part of people being "in the moment". Where I was it was the most gripped and attentive audience I've ever been in at GM by some distance.
I know there's an access issue with the video screens, some people can't get close to the stage for various reasons and do really need a screen to be able to see bands. I'm not sure what the answer to that one is. But for those who were left not being able to see, I'm pretty sure most had the option of moving forward into the crowd for an hour. I watched a few bands from the back this weekend, and without exception there were people around me chatting pretty loudly all the way through. For those I was up the front for, only NMH didn't have quiet bits punctuated by babble from behind, and it made the experience much better. Some artists are fine playing to an audience where some people are happy to have them as background music. NMH maybe don't, and it's their choice to alienate a few people to please the majority.
My feeling is that bands should make any requests like this that they want. As long as it's up to us whether we comply. It might just improve the show.