Yoz Grahame picks upon a couple of really interesting points about CAPTCHAs (those mini Turing tests used by many sites to prove you are a human rather than a bot) in Goodbye CAPTCHAs, hello Distributed Porn-Powered Processing, namely:

CAPTCHAs are a pain to users, they trample all over good accessibility practice and, most importantly, they're useless as a defense against automation

However, in detailing how some unscrupulous spammers are getting round CAPTCHAs by getting porn-seeking users to solve them on their behalf, he touches on a fascinating idea for the future:

Okay, I'm not being entirely serious with that example, but there are industries out there existing entirely to harness the power of web surfers who've lost their way. Prime example: those websites full of secondary link lists that exist purely to show up in Google results and act as a banner-loaded intermediary before sending the on their way to buy a digital camera, via an affiliate link. Popular Power - the late lamented startup that wanted to sell spare cycles of desktop computers to computationally-hungry customers - was aiming at the wrong resource. Distributed CPU cycles are worthless unless you're SETI or Pixar. Distributed brain cycles... now that's a much more intriguing proposition.

Distributed brain cycles - imagine the human equivalent of the massive zombie bot nets used by some virus writers - it all sounds like a truly distopian vision (à la Matrix), but maybe we can imagine some positive examples of how this could be used for good. We have always been intrigued by the idea of the circuit riders concept for tech support to non-profits. Could we envisage, for example, the work of a charity being put onto a massive online issue management system that pushed tasks out to specialists (legal, technical, logistics) to be solved during downtime or coffee breaks? I am sure there are better, more imaginative examples out there....