Akismet is a web service which blesses comments, trackbacks and pingbacks with a non-spam (good) or spam (no good) category. By using the WordPress plugin, you filter how other people use and abuse your blog.
I've been collecting stats from the site for a little over the week. Plotting the daily accumulation of identified spam shows a steady increase in the number of spam comments identified as well as some daily and weekly variations. I've not yet drilled down on the details - the key thing to do here is to align this view the an account of the number of posts found per day and see if the ratio of spam comments to posts is increasing, or if the increase in spam comments is simply an indication of an increase in posts.
The graph plots a point every 15 mins throught a 24 hour period, resetting every day. They look like worms.