This is a relevant and very entertaining talk: http://www.youtube.com/watch?v=rfgGNsPPAfU&feature=player_em...
http://www.google.com/recaptcha/learnmore (click the small audio icon to the right of the input box)
I turned my volume up pretty high and couldn't understand a single word over all the static in the background and over-distorted foreground audio is unintelligble. Can people actually get that audio captcha right or is that Google trolling people?