I have a request from a client to remove a user, along with all their posts on the forum. I have marked them as a spammer, and also deleted them, but their posts still remain on the site as 'Anonymous'
When you delete a user from the WordPress administration panel, there is an option to either delete all of the users' posts or switch their author to some other option. You can use the former option to remove spammer users' posts. :)
What you could do is write a plugin or some kind of extension that would integrate with akismet to chek for spam by a user and if said user is spamming mark that user and all posts as spam. Or you could have them enter something before hitting post.
