This is true for what it's worth (and you acknowledge that there may not be 'good money' in solving this problem). If you _really_ wanted a picture of yourself

This is true for what it's worth (and you acknowledge that there may not be 'good money' in solving this problem). If you _really_ wanted a picture of yourself from the expo, you'd have gotten someone to take a photo of you. So your interest (given that it comes from after the fact friend-curiosity) is right at that marginal level. If you just wanted some non-specific photos of the expo without any particular goal in mind, that's already easily done, as you saw. So what you're looking at here is people with specific goals in analyzing a photo stream but who didn't, for one reason or another, turn up and take photos to meet these goals. I don't know if you can make any kind of money - good or otherwise - from providing a service to such a marginal set of customers. The exception might be law enforcement - find some better photos of the guy who followed a woman into a bathroom at exactly 12:42, or the person who grabbed someone's purse, etc.