EclecticLip

Apparently, the images-with-distorted-text used to prevent automated e-mail signup, are being used to manually digitise sections of text archives which OCR (optical character recognition) technology can’t use.
That’s the premise behind reCaptcha, the follow-on to Captcha (which — being “Completely Automated Public Turing Test To Tell Computer and Humans Apart” — initials out to Capttttcha).

This is very, very cool — it makes the anti-spam login step bifunctional: in addition to fulfilling the intended purpose, a valuable side benefit is also provided.
Like Skype or file-sharing, it leverages an existing infrastructure.  But instead of data transmission infrastructure or computer memory, reCaptcha capitalizes on the “gatekeeping service” crucial to innumerable websites.

Very cool, and worthy of being my first polyfunctionality tag!