Tha'ts one among several things that have been discussed; I'd be up for it being that way.
BTW, it's often much more than a dozen a day; when I'm on I nuke a bunch of them as they get posted. Sometiems I catch a spammer before he posts more than the first one, preventing even more. But usually it's after they're there, and most poeple don't seem to be on at this time (1-4am AZ time), so they don't see them.
Miles nukes some too, as do others, before they're seen, I think.
There are also spammer lists that can be automated into PHPBB to either blacklist those particular members that attempt to register a specific username from a specific IP, or with a specific email address, etc. But someone would have to write the scripts to do that, and I gather it isn't trivial.
Same thing for using those spammer lists to automate diverting users into the "must be approved" list, so that not everyone has to go thru that process, just the suspect ones. Could reduce the inconvenience to legitimate noobs.
Another thing that would help is a "honeypot" forum. There are certain types of keywords that tend to attract spambots, so they either automatically post in certain threads or forums, or auto-quote certain posts that contain those keywords. The honeypot forum contains spam-triggering posts, topics, and forum headings, as well as all the other spam posts. It's possible to create scripts that autoban (and delete or hide posts from) those types of spambots. Also, it would autoban anyone posting in those forums, because any human (that reads the languages the warnings are in) would know better, as there would be a giant header on them saying "DON'T POST HERE OR YOU'LL BE BANNED" or some such thing.
Spam posts in this case probably would never be deleted, but rather quarantined in that place as bait for the other spammers. YOu might have noticed that sometimes multiple spammers hit the same thread with different spams, and it just seems to keep happening to that specific thread? That's partly how the honeypot thing works.
Though the classic honeypot forum is usually totally empty except for the warning not to post there or be autodeleted/banned.