Problem is, if the questions can be automatically generated from publicly available information (the contents of a blog), so can the answer. It will work as long as the system is not commonly available, because spammers won't care - but that's true for any new anti-spam system.

Manually creating three options and selection one as the "right answer" won't work either, a spammer will just try three times, until he gets it right.

I don't like the affinity test - it may work for certain types of sites, but consider the case where you criticize a company on a blog, and a rep wants to reply and participate in the discussion. If he has to do a "nontrivial amount of research" to post, he's probably not going to, which would be a shame.

Oh, I've come across this commenting system on mike lee's blog. Very awesome idea. Takes a bit longer to reply (and sometimes I think twice about it and don't at all), but that probably raises the quality of comments on his site. :P

Had me thinking it was serious for a moment. I particularly liked level 3 - Affinity - but there again where would all the good arguments come from.

It annoyed me that he said "feel free to correct my math," yet there is no way to contact him.

There aren't 504 ways (P(9,3)), but only 84 (C(9,3)), since order is irrelevant.

Defeat by answer permutation from a pool of IP addresses.

it sucks.. i wont do this kind of torture to my users...