Captcha

From Wikipedia:

"A CAPTCHA (a trademarked acronym for "completely automated public Turing test to tell computers and humans apart" owned by Carnegie Mellon University) is a type of challenge-response test used in computing to determine whether or not the user is human. The term was coined in 2000 by Luis von Ahn, Manuel Blum, and Nicholas J. Hopper of Carnegie Mellon University, and John Langford of IBM. A common type of captcha requires that the user type the letters of a distorted image, sometimes with the addition of an obscured sequence of letters or digits that appears on the screen." (http://en.wikipedia.org/wiki/Captcha)

According to an article in Forbes, 150,000 hours per day are wasted on filling in such fields, time that could be better mobilized in projects such as ReCaptcha