http://bmaurer.blogspot.com/2007/05/recaptcha-new-way-to-fight-spam.html "reCAPTCHA: A new way to fight spam".
:"Installing is as easy as adding a few lines of code to your HTML and then making a HTTP POST request to our servers to verify the solution. We also wrote plugins for WordPress, MediaWiki, and phpBB to make it very easy to integrate."
At least if we ever need to enable CAPTCHAs on a large-scale basis, we might get some good out of it for WikiSource.
-- Gwern Inquiring minds want to know.