CyborgCaptcha - Completely Automated Public Turing test to tell Computers and Humans Apart!
What most CAPTCHA's do wrongly is they don't just test, but they make bad assumptions. This capture actually has a different but more accurate approach.
AI's are "too stupid to get it wrong" and humans are "too stupid to get it right", so both are more often satisfied by this CAPTCHA than alternatives.
- Julian