Referer spam
Wow, we opened up http://www.zimoblog.com today at Zim, and within hours I've gotten my first Referer spam. I'm pinging www.weblogs.com whenever someone updates a blog, so it must be someone polling there (perhaps the http://www.weblogs.com/changes.xml file) and just hitting links with a bogus referer, hoping that the site will display links from external sites (many blogs sites do).