Yep; i first heard about it a few days ago, but have now encountered it…

Referrer Spam

Some crawler at 211.152.14.98 just walked my entire Blog comment tree (I suspect that it knows about blosxom) and my non-web-accessible logfile shows that it is trying to poison the referrer field with pr0n URLs, in the hope that somewhere I would leak the data to the net thereby getting Google to boost the pagerank of the target site’s content.

The last thing it did was set a “cookies.asp” URL in there too, presumably so it can track usage/effectiveness…