I wave for the simple reason (morbid?) that no matter your reason for riding, you are riding. All rides for any reason further our sport. Some (squids) detract as much as they add but anyone riding is a participant in the incredible activity which makes me happy everyday. The fact that they are out there that day and I see them makes me want to give them some sort of recognition. So I wave. I may not like them if I were to talk to them but I do like them the moment I see them!