Spambots. Hundreds and hundreds of spambots. The administration wanted to cry.
We've changed the software we're using to something less... well, something less likely to be taken over by links to all sorts of products. For every spambot countermeasure we put in, we'd just get more spambots. We'd delete accounts that weren't made by humans, more would be made. It was like everything on the internet that made us sad was coming to live with us.
We're sorry you have to reregister. Trust us, this minimal pain is worth it.