I always wave to people in the opposite direction and if someone passes me on the left I will say hi, they usually use hi when passing instead of, on your left, around here. Then there are those serious riders who check out your bike - look you up and down - visiably - then ride on w/o saying hi or waving THOSE are the ones who piss me off, I usually offer a few words, they can't hear me but it sure makes me feel better.