Katie O'Beirne has an idea so simple it's downright brilliant. She leaves a disposable camera in the park, tied to a park bench with a twine, and then waits to see what develops.
She posts the wonderful photos taken by random strangers on her tumblr blog New York Shots - via Kickstarter blog (with video interview of Katie)
Or maybe I'm being too pessimistic.
http://theplug.net/28/strangerphotos.htm