" i often see bicyclists on the road and want to yell out, 'rock on!' or something less cheesy and more supportive. but anything said out of a moving car sounds mean, sarcastic. who can tell friend from foe in a car passing at 30 miles?"

True, truem all yelling sounds hostile from a moving vehicle.

Funny thing is that the one (so far) time I was actualy yelled at from a car the guy had a bike rack on the rear of his SUV, in Marin County no less, yelling at me that I was supposed to ride on the sidewalk. I was in the bike lane at the time

Also back to the orriginal subject, great thread, thanks for starting it, it's great that we all "get it" here.