Last May I posted a concern about the 50% failure of CAPTCHA. Only one of the two words were actually checked to validate a user as human so entering random data worked half the time.

A few days ago a full disclosure post announced a 100% CAPTCHA failure.

Google’s reCAPTCHA is currently broken. At the moment, you may follow these
steps to complete a CAPTCHA without user-input:

1) Click the “Play Sound” button
(javascript:Recaptcha.switch_type(‘audio’);)
2) Enter any sentence comprising of 10 words (“google google google google
google google google google google google”, as an example).
3) “Answer Correct!”

http://www.google.com/recaptcha/learnmore