I've been fighting spam on the backend for the last while. (Limited hours due to personal illness + work catchup sadly). I *think* we are finally clear of the worst of the sources of spam now so I've reactivated the account creation options. You should be able to get to those here: http://planewalker.com/user/register
I'm going to keep an eye on the postings for the next week to try to kick out any more spam sources as we see them.