Just an FYI that I'm aware of and actively combating the spam issue we've seen on and off. I've set the board up for the time being so that I have to manually approve new registrations. Most mornings I wake up to 20-30 registrations, 99% of them are garbage spambots.
I'm working to learn phpbb well enough to implement some antispam techniques. If anyone has done this before, let me know!