Phones and photography are banned in many Berlin clubs - they either lock your phone away at the entrance or put a sticker on the camera. That's why you barely see any footage from inside Berghain anywhere...
"Se non è vero è ben trovato" but this reddit post [1] does a decent enough job of explaining what's happening there (or what cool people think it might be happening in there). Slightly NSFW text post:
It is, and that's what it's intended as. Some shows in the US do it too. e.g. Lane 8's This Never Happened shows in Oakland. But the most recent version of that had a lot of people complaining that there were lots of phone camera usage, so the sticker thing might not work in some venues.
Thing with sticker is that usually you go to the toilet and walls are covered in those stickers people removed from their devices as soon as they got away from the bouncers.
The point is that the sticker would have to be taken off deliberately. If you are caught taking a photo, you can't claim you just forgot about the rules. You broke the rules on purpose and depending on the club they either get very angry with you or kick you out without warning.
The stickers you see on the walls could have accumulated over month. The system usually works fine and you rarely see anyone taking photos. Certainly way less than in clubs without those stickers.