Yeah. My first thought was "have fun smuggling any kind of bulky electrical equipment into a Taylor Swift concert, let alone a stage light. Security will not even be mad."

But on second thought, I think there might be an actual scenario to worry about: Activists hijacking the system to show political messages.

For that they'd "only" have to beam the IR to a small spot of the room (but with much higher "resolution" than the normal effects). As long as the symbol/text/whatever is still legible enough that people recognize it and can take pictures of it, they'd have achieved their objective.

Something like this might be possible with a much weaker, purpose-built emitter that could be hidden under clothing. Too much risk and effort for some dumb dick joke, but thinkable if people have some kind of political motivation.

As a "bonus", the first blame would probably fall on the unfortunate people whose wristbands lighted up with the message, while the real perpetrators - the ones with the emitter - remained hidden.

There is an easy fix as well though: As the system "paints" with digital signals and not light, the old lighting rule that colors mix only additively doesn't hold anymore - so you could add a "don't light up for the next 10 seconds" command to the wristbands and just have the stage beam that command continously whenever no effect is wanted.