I usually do, and initiate it - a very old habit from when we were a small minority - with a brief one up from the grip. Half respond, and a few Harley guiys are beginning to respond, but with a subtle one down from the grip. Other locals are waving downwards, but I've tried it and it's too awkward. I don't initiate to no-helmet riders, or to unmuffled bikes, and I doubt they know the difference.
 

This is one of those weird "culture within a culture" things. I think whether a rider waves or not is determined by his approach to motorcycling; is he alone on the road or is he part of the gang? I find sportbike & Harley riders tend to think they're solo, forging into the unknown, just them, the wind, and the road. The rest of us are somewhere in the middle - part of the larger culture of motorcycling. Those that understand we all enjoy something in common tend to be wavers I think.
 

Yes, I wave using the inside arm, extended toward the ground.