Ok our anti-spamming precautions are this..
1. Vigilant Admins (well done Sy

)
2. Enforce Email Verification (stops using fake email accounts)
3. Enable Visual Confirmation (stops most bots)
4. Block well known spamming domains - *.mail.ru / *.inbox.com etc
5. Block well known spamming IP Ranges
6. Some other stuff
7. Keep phpBB patched, but also remove the version number so spammers/hackers searching for exploitable versions online dont get you in the results.
I've recently found some php scripting that I use on a friends blog which looks at information about the browser/bot searching/using the site, and decides wether it's a spammer or not. For instance if a bot says it's 'google.com' it checks all the details and IP's etc to confirm it is actually google.com before letting it near the site. This will be getting integrated into when im able to find the time to do so.
The recent spate of spam has been from @*.info domain's it's possible to add these to the black list and require the person to contact admins to manually add their account due to volumes of spam.
Remember to block the domain of the people spamming you and add their IP address to the block list (do a DNS lookup first to make sure you're not banning AOL.com or soemthing) Due to LEC's diversity in members we cant be as harsh as blocking entire countrys from visiting the site incase it is a legitimate user.