Commenting is just a spam magnet
I was at a talk last week where a blogger encouraged people to allow commenting on their sites. I have always allowed moderated commenting on this site and I use a WordPress plug-in to dump obvious spam. The plug-in has been averaging 600 spam catches a month. Of the very few comments that make it through the filter, most of them are spam too. I am glad to see my opinions are so valued in the spamming community!