I believe the answer is "don't record at a concert because it annoys everyone else and the video is garbage anyway".
I'm not surprised that they have not implemented this. It would take about five minutes for someone to reverse-engineer one of the beamers, and then about five more for someone else to turn it into something you could hang off your keyring to mess with people, and about thirty seconds after that to produce a huge consumer backlash.
Youtube is already full of good quality concert videos free of charge. People still film concerts. I don't know how to 'fix' this.