At the moment we've got a lot of checks to try and prevent spammers. It seems like its falling on the side of causing problems for real Moodlers.

The registration system doesn't have an open web form and if it is going to be attacked by spammers - it'd be a targeted attack.

More to the point, all of our current detections of real Moodle sites could easily be circumvented by spammers hosting their spam on a real Moodle site.