From my experience last year, it gets very dark and very hard to find people after a while. And nobody's going to want flashlights in their face.
Which is more to say, meeting beforehand and forming small groups is better than wandering solo hoping to bump into anyone you know.
Failing that, wearing forms of glow that are unique enough to be recognized without seeing a face is also good.
@emanate @mawr Thanks for the heads up. I'm going to try and figure out a specific place for our various group members to meet up.