I've added some additional security to stop the recent spam thats appeared. It shouldn't affect existing or new users, however should stop all the automated advert guff thats appeared.
The spam has come via a tool that uses a database of open proxies, so can't be blocked by IP. I have however dumped their database and am about 70% (will take a few hours yet) through closing the proxies... basically I don't expect much more spam of this type.