When I switched to drupal, I lost the “type in my first name” code to stop comment spam that I had written for Movable Type. I used drupal’s systems for spam spotting and comment moderation, but in fact those are not very good yet, so I re-coded the system so that anonymous commenters can comment directly if they answer a simple question on the comment form. The question, in this case the trivial one of entering my first name, is easy to answer and can be handled by the blind (which is not true of captchas.) If spammers should write programs to fill in that field, I can quickly change the question or make it more complex as needed. If spammers start to automate answering trivial questions faster than we can think them up, then perhaps we can consider captchas and other more advanced turing tests.
Note that you won’t see the question if you are a registered user of this site (you can also log in with your idea from most other drupal sites too) so registration is encouraged but not required.
Comment spam is a nasty scourage. I think Movable Type as the most popular software gets the most but all systems that get popular will get hit. In addition I modified drupal to use the rel=nofollow tag on homepage links — it already does it on other links in comments — so spammers gain no search engine credit for their spam. Sorry, that also applies to honest commenters.