I did a lot of partying around NYC (pre baby) where this rule is rare. There are usually close to 50% of the crowd taking selfies, putting the phone in the air to "record" the DJ, or generally scrolling through instagram instead of dancing. I thought this was the norm, but then I spent a summer in Berlin. There, people actually dance, and are there to appreciate the music. The vibe is so much more fun because everyone there is contributing to the energy by actually having a good time, instead of being preoccupied with showing people who are not with them that they are having a good time. I think nightlife in Berlin is so much better than NYC because of a combination of the cell phone rule along with the stricter door policies, and I hope those come to NYC by the time my kid gets old enough for me to be able to go out again.