I like it -- a CAPTCHA for stupidity.

You could do pretty simple problems (like the Project Euler stuff), with a few random elements to keep things interesting -- especially because the smartest people would come up with shortcuts and be able to post more frequently than those who solved it by hand.

This is a great idea from a publicity standpoint. Journalists will eat it up.

I will definitely throw this in for one of my upcoming sites.. Are you thinking of building an entire site around it?

edit: see how all of the negative publicity really positively helped hotenough.org recently.

sounds like a pretty boring place to hang out.