We were out for a walk not long ago and saw a man picking up his dog poop in the street. Happy to observe this, and about to commend him, he then threw the poop AND the bag into the street. WTF!? I maybe not so nicely pointed out that the best place for the bags was in the garbage can and he should pick it up, and he told me that if it bothered me so much that *I* should do it. I retorted that the poop was his, not mine, but it didn't seem to phase him. Ridiculous.
My boyfriend has been known to see people throw garbage out of the windows of their cars, etc., and while on bike go back to pick it up and return it to them saying something along the lines of "hey, I think this is yours!"
ETA: I have seen a lot (a LOT) more people cleaning up their dog poop since I arrived, and the problem is *much* better than it was in '06. I just found it crazy that this guy made the problem worse by wrapping the poop in plastic and then throwing it in the street, meaning it wouldn't dissolve in the rain, etc.