Brilliant Idea
Fight Spam, Digitize Knowledge. This is an idea that slightly tweaks Captcha technology to show two words, one like the normal captcha but the other a real word that will be translated from a scanned book.
To me, this is the ultimate play on Micropayments - users who want to comment on an article, doing a very small chunk of work. User-generated Mechanical Turk, if you will.
This double-duty doing captcha makes me think there should be a way for elitist sites to screen who can leave a comment by asking specific questions as a type of a captcha.
put a simple algebra question like “Solve for x: 3x+2=23″ and they have to put the answer in to be able to submit, comment, whatever. that way you can ensure those commenting have at least a 7th grade math level. other questions could be music, movie, geek related to screen unwanteds AND spammers.