Chris Albrecht at GigaOm writes a story about a Luis von Ahn (Assistant Professor of Computer Science at Carnegie Mellon University) who is one of guys who developed Captcha technology.
The story is about how NY Times is using CAPTCHA technology to fix errors that crop up in their effort to digitize old issues. I put together a schematic to explain what they are doing.
As you can see whatever words OCR (Optical Character Recognition software) could not recognize well enough are handed off to reCAPTCHA which sends them to various websites to be used as “challenge words” for spam protection. When humans decode them as part of their “response” to “challenge words” they go back to the database as “error fixes”
This story for me is simply an example of brilliant use of leverage. You are breaking down the problem (OCR errors) into small pieces and parceling them out to individual websites. These individual problem pieces are part of a SOLUTION to a different problem (spam protection). People are engaging in solving the first problem as a side benefit of solving the second problem – meaning at no cost at all.
You can read the whole story here:
CAPTCHA’s Can Be useful, Don’tcha Know