I'd like to suggest that Akismet detection of user profile fields cause the user to be placed into the Moderated User queue. From what I can tell, right now the integration with Akismet will simply strip the user's signature out if it matches their spam signatures. That's an effective way to prevent the moderated link from showing up, but it's not very effective at actually bringing attention to the offending user unless you're monitoring the spam trigger logs and then manually searching for the user accounts. I'd much prefer that a user detected by Akismet be placed into the users awaiting moderation queue. That way there's an obvious flag in the admin bar that allows people with the right privileges the ability to remove the user entirely.