I have been getting hammered with comment spam, but have been using Jay Allen’s MTBlacklist with pretty good, if not perfect, results.
The other day I got sick of it and started looking for another solution, and renamed my comments file, following the instructions here.
Since renaming, I haven’t gotten one piece of comment spam. Comment spammers are in it for the volume, and so just hit everyone with the default-named comment files.
So, go forth and tinker, and leave the spammers behind. For now.