There were more than a thousand registration attempts in the past month, so I suspect the registration system was not doing a very good job of weeding out spam bots. All registrations have been rejected. I switched the registration system to email confirmation. It probably won't help much, but if you tried to register in the past month and still haven't been approved, try again and you should be able to confirm yourself now. I'll try to manually manage spam users by deleting their accounts for a while. Just don't post anything that looks like spam.
Edit: I think confirmation (and all other) email wasn't working until I finally noticed and fixed the problem today. You should now me able to register and confirm your own account.