I guess evryone running a weblog knows the problem, porn sites (but also others) are spamming the referer page, to get a higher page rank at google.
My weblog is hosted by antville.org , I guess among the free weblog services it's the best, but untill know, they don't offer any solution to this problem. User of www.movabletype.org are starting to use black-lists, but most of the spammers are using the free blog service blogger.com and it takes only a few seconds to create a new accout which is being used to spam other accounts.