There seem to be some fairly easy ways to deal with comment spam.
Of course, you could do what I detail at http://trikuare.cx/mt/archives/000425.php but that’s a bit of overkill for simple spam killing (I had other reasons to want to move to phpBB), but for a few days as an interim solution (which seemed to work well according to my logs) I did: http://trikuare.cx/mt/archives/000410.php
Anyway. Some of the comments on that thread were pretty funny. Like how the spammers seem to think that weblog authors aren’t actually clamping down on spam, and that the smarter ones aren’t figuring out simple ways to make their efforts useless anyway (for example, adding phpBB’s memberlist.php and so on to robots.txt), not to mention they’re not figuring out that all they’re going to do is cause more problems in the long run.
I’m very tempted to post to one of their threads about how if they really want to direct people to their site, maybe they should make a well-constructed site advertising things people ACTUALLY WANT TO BUY, since that’s always going to be the guaranteed best way to show up in Google for pertinent search queries (and why they want to spam non-pertinent search queries is beyond me, since all it does is lower the value of the Internet as a whole).