Technical note on the terminology here. Just FYI, this is not strictly speaking crowdsourcing. Just like outsourcing refers to replacing local workers with workers in a foreign country, crowdsourcing refers to replacing people who have a job with generic members of the public. Amazon's Mechanical Turk is crowdsourcing.<p>von Ahn's area of work is in <i>human computation</i>, which specifically refers to the augmentation or replacement of some part of a computer-based computation process with human calculation. CAPTCHA is a good example of human computation, because it augments the problem of OCR by sourcing the identification of OCR-hard characters to people on a massive and automatic basis. Human computation allows you to formulate algorithms that are too hard for computers to do and too laborious for people to do into a sort of "average" between the two. This gives you a lot of leverage and allows you to do some neat stuff, like the above.<p>If you didn't know, von Ahn's main claim to fame is having founded re-CAPTCHA and then having marshaled the company through a successful Google acquisition. After that I think he became professor at CMU, where he is currently.<p>EDIT: a more scholarly examination of the differences between human computation and related fields is here:<p><a href="http://alexquinn.org/papers/Human%20Computation,%20A%20Survey%20and%20Taxonomy%20of%20a%20Growing%20Field%20(CHI%202011).pdf" rel="nofollow">http://alexquinn.org/papers/Human%20Computation,%20A%20Surve...</a>