captcha is easy to break

Jay Allen (author of MT-Blacklist) weighs in on the arms race with spammers:

If you use a captcha, spammers will use OCR. If you make them answer a question, they'll collect all of the questions and answer them one by one, or even better, post the question on their own porn sites as a "bot protection" question on their own sites, hence programmatically getting an answer from another human.

That last part should have you scared. He's right, CAPTCHA is completely vulnerable to man in the middle. Another good reason to dump CAPTCHA and find something better.