I came across a very nice article on businessweek.com about this guy Luis von Ahn who has figured out a very clever way for harvesting community efforts. Luis was instrumental in creating the Captcha, the system that throws out an image of a word the letters of which that one has to read and type it in to prove "humanness" at websites. The system is based on Luis' thesis and is very efficient in keeping out bots from logging into websites or spambots from posting spam on online forums. Major websites including yahoo and google use this system to keep out bots.
Apparently, Luis figured that as so many internet users were interpreting images of words and transcribing them it could be employed to convert digital scans into text. What a wonderful mechanism to harvest users for innovation. I remember playing image identification games sponsored by Google when their image search facility was being launched. Clearly, this is good news for people thinking on innovative ways of tapping into the crowds!