Light shows are easily
performed and are quite enjoyable when one is
in the mood for them - the problem arises when one isn't. Often, a
newbie raver will realize he can cheer up all the other
rolling ravers by rotating and moving his wrists while holding
glowsticks and then applies the first false rule of an ecstasy high: "I'm rolling, therefore everyone else is." Following this train of thought, said newbie will not hestitate to come up in people's faces and start
flashing his lights at them.
What I have so far failed to mention is that coming down from an ecstasy high can be a fairly pleasant experience. You sit back, talk to your friends, maybe lean up to a nice girl and take in the vibe, letting the high slowly drift off, enjoying in the fading end of it. When directly stimulated, as through the use of glowsticks, the high might kick back in for a second as you focus on the lights, but their absence and your now agitated state will make the comedown more edgy. Hence, lightshows in this state are unwanted.
So, if you ever are at a rave, and you want to give out lightshows (please do!), dance with your lights and see if anyone actively follows them. Walk up, come closer to their face and give a questioning look. If the person wants a light show, they'll let you know. In the chillout room, just turn them before you and wait for a reaction.
But don't start blinking your keychain laser pointers in a perfect stranger's eyes. It's just rude.