I was browsing around some photo sites I used to frequent and stumbled on this site. I had this exact idea a few years ago. Spider the web, finger print all the images you find, then let people post their own images and search for duplicates. It’s a great application with so many possibilities. Should have spent more time on it I guess. They seem to have done a great job though. Super fast too. I have a few feature options that I was going to implement in my version, so maybe I’ll just forward them along.