Anyone who has tried to create an account in any of the portals these days would have seen CAPTCHAs these are the wiggly words that google and yahoo use to keep out the bots. Generally CAPTCHA are anything that does that trick, not just a wiggly piece of text. http://www.captcha.net/
Would be an interesting thing to try and break these stuff.
One of the ideas currently doing rounds is research blogs. http://hunch.net/
is a good one for machine learning. They are also planning to make it a place where people put up links to papers they like and which they think are worthy compared to the other millions that gets published just for the record.