Viper007Bond
says
Unfortunately while the concept itself is clever, the CAPTCHA is very trivial to break. So much so that I threw together a PHP script just for fun that submits fake spam to your script’s form every time it’s run. 
If you’re interested in the source, you can find it here:
http://www.viper007bond.com/2009/09/30/breaking-click-in-that-captcha/
