UPDATE: http://www.boiledbeans.net/2008/04/04/reverse-turing-test/

Older post:

In order to keep off script kiddies from posting spam comments, we have added a math based captcha which shows up when you try to post a comment while not logged in.

Here is an example question which will appear on April 1, 2009:

On all other days, the questions will be as simple as “add 5 and 5”, which as a quizzer, should not be hard for you. But in case you forgot addition, keep some abacus variant handy ( Google is also a part-time abacus variant.. it has a calculator built in :) )

If you detest captchas, please register and the annoying first standard addition questions will vanish :)