Yup, spam bots.
99% of them get as far as registering (which is why they show up as logged in users), but their accounts are put in "moderation" by our automated checking mechanisms, meaning they have to be manually approved before they can post.
We have nearly 80,000 of these users ... I should start purging some of the older ones at some stage I guess, I keep them in the database for reference for matching IP addresses and such, but that information does go stale after a while, so it's only valuable up to a point.
The main additional work I have to do is deal with the false-positives where our automated systems block legitimate users - I have a standard routine for verifying people, but it does take time. Fortunately, 99% of spammers don't ask why their account has been blocked from posting.
