As as attempt to combat the increasing amount of spam and spam accounts on the forum we have taken several measures:
1. We have deleted all member accounts with 0 posts. A large number of these were spam accounts. Apologies to those who had registered an account and never posted.
2. Improved verification questions.
3. Blocking of some IP ranges.
We haven't yet enabled manual verification of all new accounts, but if the above measures don't stop the spam this is next.