Have you ever noticed how, when two guys on motorcycles pass each other on the road, they almost always seem to exchange this two-fingered wave? When I first noticed it I assumed they knew each other, but soon I started seeing it so often I realized there was no way all these guys could know each other. I was surprised and jealous.
There's so much in life to keep people apart. Strangers passing might have more in common than a married couple or lifelong friends, but they'll probably never even say hello because of some unspoken human crankiness that says strangers don't say hello. But these motorcycle guys (and women, presumably) have gotten past that. They've got some kind of instant bond, formed out of nothing more than the fact that both rode vehicles with two wheels instead of four.
Well that's kind of what I feel when I walk past another guy with a beard. There exists (at least in my own mind) a kinship between myself and every other guy who is capable of growing hair on his face and does so.
Except guys with goatees.