Blog comments spam?

What’s going on here? This pre­vi­ous post’s com­ments now, as you can see for your­self, includes what seems to be the usual email porn spam. Of course of less value as MT strips the html (orig­i­nal com­ment includes links). Has some­one real­ized the value of hid­ing their dirty spam in the blo­gos­phere because of the good search engine rank­ing? Or is it just plain teen fun; adding obscene mes­sages to ran­dom people’s blogs? Once in a while I have to erase such bril­liant stuff as “Die!” and “Fuck you” from the com­ments around my blog, so actu­ally I thought it was just a prank, but it keeps turn­ing up…

Update: As read at Dan Gillmor’s eJour­nal I’m not alone…
Update II: Not alone at all — but Kalsey’s got some ideas on how to pre­vent it.