userland has the same problem with porn spam in the referrer listings. dave thinks their intention is to leech off a site's good page ranking. maybe they simply try to fool site owner or visitors from google to click on their links.

however, dave suggests a robots.txt file. i'm not sure about it but you could easily install one on antville.org and see how it works. i reckon sooner or later they will come back via backlinks.

btw, in case anyone wants to become a hero in the blogosphere, go and implement a referrer spammers database complete with a nifty xml-rpc interface ;->