Are the spam members actually posting (this is the first forum I check when I log on)? If they are, someone else must be deleting them. If they aren't, no big deal as I have been deleting members who have been inactive for a year and have 0 posts (granted, that means they don't get deleted until 2011, but again, if they're not posting, no big deal).
If I do come across a spam post when I'm on here, I delete it and its poster immediately. Which is why if someone else is just deleting their threads and not the poster, I wouldn't know about it and not delete them either.
It hasn't really been that much though. I've been keeping an eye on the member count and it's only risen by about 10 members in the last couple of weeks. I wouldn't necessarily call it a "flood".
There is an option on this version to allow mods to "approve" new members before posting, I believe... I think we didn't turn it on for danny cheung because it wasn't that great of a problem... he posted once a day, we just deleted. It wasn't like he was registering every hour and posting, for example.