I wave, and sometimes get a response, sometimes no. I did have a dude all decked out for the roadie parade come up behind me when I first started commuting-I was trying to pus through a climb, and was struggling a bit, and instead of blowing by me, he stayed behind me and offered morale support-he asked how long/why I am riding, what I thought about it, how my experiences were, etc. Before I knew it, we were at the top of the hill. He flipped it into high, shouted 'there you go, no problem!", and dropped me like a bad habit.