I find it bizzare that strangers would wave at each other. Plus, I'm cycling - traveling from point A to point B. Unless you need to communicate something important, you should NOT wave or speak to me - if you do so you are causing a distraction which itself could be problematic.
Hidden pothole? Crack in the pavement? Road-kill up ahead? Sure, give me a signal, that would be appreciated. Just another of the two dozen or so cyclists I will pass on my commute home? Reserve signals for important things, like indicating turns!