I just thought of posting this topic last week. There a few guys with scooters that ride close to my house and seem to be commuting at the same time I do a lot. I don't really wave at them because (this might sound mean) they seem like huge dorks. Not that I think I'm that cool, but I just don't think they care about being part of the cycling community or waving. There seems to be 3 types of scooter riders around here:
1) The high-water pants, pocket protector wearing old guys who are probably doing it for the environment and to get good gas mileage even though they are rich as hell
2) The 300+ pounder commuting to work to flip burgers and just sqaushing that little thing
3) Little rich girls that think they look cute on it
All the same, I'm going to start waving and see how it goes. I'm guessing they will be confused, but that's fun too!