If I say much more, I'll probably say too much. So, my short rant is this: Be a good pet parent and neighborhood steward by picking up your dog's (or other domesticated animal's) poo from the sidewalk. Those that enjoy using public sidewalks to exercise, don't enjoy cleaning poo from the bottom of their shoes.
(Last night I spent 30 mins cleaning up dog poo piles from our backyard without stepping in anything, only to go for a quick 30 min run around the neighborhood and come home with the bottom of my shoes caked in poo. Just ask Todd how mad I was about that!)