There is an interesting talk on Google Video by Luis von Ahn. He talks about using games like ESP Game and Peek-A-Boom to label images to make image searches more efficient and accurate.

However, the thing that struck me the most was how spammers break CAPTCHA.

  1. Spammers hire lots of people in countries where labour is cheap to manually input the CAPTCHA the code. This is not so bad because it hurts the spammers as they have to pay and on the bright side, provides much needed employment.

  2. The other method is more evil. Spammers run a parallel porn website which grabs the CAPTCHA image and displays it to the eager porn visitor who inputs it to view a free picture thus helping the spammer to break the CAPTCHA code.

Watch the video, it is interesting and informative.