We live in a dense neighborhood where everybody is expected to clean up after their dog. I started cleaning up after the occasional mistakes of others, too, and that quickly expanded into cleaning up other litter. Heck, I've already got the bags, I'm picking up worse, and since we're using the neighborhood as a urinal, we do owe something back. It's rewarding. People notice this, it's contagious (maybe we can start an epidemic), and reflects well on dog people. Bad for the ego problem though -- it's already tempting to feel morally superior when you've got such great dogs.... :-)