A Spanish town called Brunete used volunteers to covertly identify people who had left their dog's shit on the public sidewalk (the volunteers chatted up the dog owners' about their dogs' breeds, this was cross-referenced against the register of dogs). The volunteers then packaged up the turds in a "lost property" box and returned them to the owners. 20 volunteers delivered 147 crap-o-grams and reported a 70 percent drop in public poop after the program ran (they did not disclose their methodology for calculating this).
On the one hand, this is funny. On the other hand, it's a sobering reminder of how trivially small pieces of seemingly innocuous information can be used to identify people. On the third hand, people who let their dogs crap on the sidewalk and don't pick it up are the worst human beings on Earth, and I join with Mark Thomas in calling for a law that requires people to wear any unclaimed turds as a mustache for a full day.