I think littering qualifies as an anti-social behavior. It's one of my pet peeves. I am super careful about my own trash (I carry a plastic ziploc baggy in my seatbag when I ride) and I pick other people's litter up if it is not too gross (once I happened upon a used condom right in the middle of the bike path! Who does that! But that was one thing I wasn't going to pick up).