reCaptcha - Block spam and digitize books(techcrunch.com)
techcrunch.com
reCaptcha - Block spam and digitize books
http://www.techcrunch.com/2007/09/16/recaptcha-using-captchas-to-digitize-books/
http://www.techcrunch.com/2007/09/16/recaptcha-using-captchas-to-digitize-books/
http://tinyurl.com/2wtrco
Its interesting to note that given the usability constraints of captchas people will almost always go for a "more usable" and algorithmically complex alternative if one is available. The use of akismet to stop comment spam in blogs in a case in point.