Six Apart released a patch to MT 2.661 and 3.x that fixes a hole which would allow evildoers to send email to third parties. Unfortunately, the patch is not promised to be compatible with lower versions, such as 2.64 which is what I'm running. I purposefully didn't upgrade to 2.66x because I didn't like some of the new improved features. And I didn't go to 3.x because some of my favorite plugins won't work there and it would require some redesign of the site, which would take time.
But it's increasingly clear that I'm reaching the end of the line. Sooner or later I have to either go to 3.x, which is hard, or to WordPress, which will be a very very hard conversion, especially for the archived posts.
I have other things to do.
Meanwhile, I've loaded up the patch despite the lack of warranty. Please drop me a note if something seems weirder than usual.