Referer spam

[Mastiff]

I don't know if this is exactly the right place for this, but has anyone figured out how to deal with referer spam?  I've been reading up on it, and I put a huge blacklist in my .htaccess to block some of them, but it looks like they are already stepping it up to the next level and using mis-spellings and stuff, same as E-mail spam (e.g. one referer is "http://.../pocker-table.html").  My logs are jammed with this, plus I have a lot of extra "guests" reported as being on the forum all the time.

The only fool proof thing I can think of is to actually check the referring page to see if I'm linked.  Some of the blog packages have add-ons to do this.  Anyone done such a thing for SMF?  I wouldn't really know how to code that up myself.  Since my forum is fairly low traffic, I don't think the server would notice, but I realize this isn't the ideal solution because of the overhead.