It seems that the effectiveness of Akismet for comment spam protection is starting to wane. It still catches huge amounts of spam (need to clear another 1600 spam comments from my cache in Wordpress after I write this) but slowly but surely spam comments are sneaking in.
It seems that spammers are learning that cramming a post with dozens of hyperlinks will always bounce back, so they’re increasingly settling for comments that contain no additional links, and simply inserting their spam URL into the website field. It seems that the random comment content is just too obscure for Akismet to detect.
My attempted solution has been to deploy Eric Meyer’s GateKeeper plug-in and I’m afraid you’ll now need to tick a box whenever you leave a comment. I’ve made it as unobtrusive as I can (using a checkbox rather than a text field).