EE’s blacklist didn’t seem to do jack for trackback spam. Twelve hours after turning the blacklist on, I had 33 more of the bloody things. I checked the EE forums again, and found reference to a setting that randomized the trackback URL, and authorizes each URL for only one use. This seems to have done the trick – about 24 hours after turning on that, I’m still trackback spam free.
UPDATE: As of 7/1/05, I’m no longer running EE.