Spam is not limited to email. (Background: the way Google works is sites are rated higher in results based on the number of other sites that link into it, so it is to your advantage to have other sites link to yours.) Every week or so some slimey site will come along and post a “comment” on one of our blog entries from, oh say, MARCH with a link to their site, thereby gaining a free link to their site and better PageRank in Google. Some folks are dealing with this using a shared BlackList, and we are currently just not displaying URLs in comments. I ran across this hilarious account of someone’s attempt to bill a blog spammer for unauthorized advertising. I think this will be my newest strategy!