[gregory80]

> "can't be cracked"

Not sure about that. Certainly tough, but crackable.

http://stackoverflow.com/questions/448963/has-recaptcha-been...

http://www.allspammedup.com/2011/01/google-recaptcha-cracked...

[w1ntermute]

It looks like they've artificially weakened it:

> reCAPTCHA uses a “one-off” system. That means a letter in a word can be incorrect, and it will still be accepted by the system.

[woodall]

It is also only verifying 1 word out of the pair; usually the more garbled one.