I've been thinking about it, but I can't find another reason. When I moved to my new server two months ago on this very day, I was forced to remove the Captcha! plugin after having rebuilded MovableType on the new HP-UX server. Because of security issues Verio does not allow (yet) the installation of the Perl Image::Magick module on HP-UX hosting plans. This module parses the little PNG with the security code commenters had to enter before being able to comment. I know there are more options - MT BlackList, renaming the comment and the trackback cgi's, IP-banning - but, although initially I felt quiet naked without Captcha!, I decided to keep the comment system open, and see what would happen. There's only one protection running now; if a bot starts to flood, after a few comments in a certain number of seconds the IP-number of the commenter is automatically banned my MovableType, and that happens every once in a while.
That's all, so I was wondering what the heck and why. Why I'm I not bothered anymore? Must be SpamPoison then, wich has nothing to do with comment spam, but everything with spam harvesters.
The Spam Poison links will redirect email harvesting bots to trap sites that will feed it with an almost infinite loop of dynamically generated fake email addresses, mostly on known spammer owned domains :-) This will render their harvested lists pratically useless and of no commercial value, while it will pollute their databases in such a way that they're out of bussiness for at least a while, because they have to clean up their databases.
Now, I'm I right? Is SmamPoison working so good that the spammers have started blacklisting blogs with SpamPoison links?