Google, LiveJournal, MovableType, Yahoo, Microsoft, WordPress, Haloscan, and a few other companies have joined together in an effort to kill (or at least, maim) comment spam :

If you’re a blogger (or a blog reader), you’re painfully familiar with people who try to raise their own websites’ search engine rankings by submitting linked blog comments like “Visit my discount pharmaceuticals site.” This is called comment spam, we don’t like it either, and we’ve been testing a new tag that blocks it. From now on, when Google sees the attribute (rel=”nofollow”) on hyperlinks, those links won’t get any credit when we rank websites in our search results. This isn’t a negative vote for the site where the comment was posted; it’s just a way to make sure that spammers get no benefit from abusing public areas like blog comments, trackbacks, and referrer lists.

For MovableType users, you can get more technical details here and the plugin to help support this new tag here. All you need to do to install the plugin is upload a single file to your webserver (you don’t even need to edit the file’s permissions), so if you’ve got a moment to spare, please add this critical update. This might not make spam disappear, but it’ll certainly take away a lot of the incentive for spammers to flood our sites.