I have enabled the authimage mod for WordPress, which requires you to input a sequence of characters that are displayed in an image when you wish to comment on a post.
This effectively prevents spambots from hosing the comment system, and has allowed me to remove moderation and re-enable comments on the weblog. Feel free to leave your mark, and go down in history as having contributed to something that's completely useless.
A testament to open source - if there's a problem, *somebody* will be able to adapt and overcome it without having to wait for a vendor to make things do what you want them to.