Good news -- I've (after
much pain and suffering) got us set up with an SMF plugin that will check the IP address, username and e-mail address of new members against the
Stop Forum Spam database of spammers. If it finds a match, then admin approval is required; for everyone else, they can get in with only e-mail confirmation from them. I've also turned down the difficulty of the captcha on signup, as it was hard to read sometimes.
I'll keep Lord Dave as admin for the time being, as I don't know how effective this is going to be. We may have to roll back to admin approval for all accounts if this plugin doesn't catch everything we need it to, but I have high hopes.
Oh, and because SMF is horribly broken, this verification won't work for IPv6 clients. If you're on IPv6, your account will still need admin approval regardless.