Re: BuddyPress Spam
Hey wordpressfan, understand that BuddyPress runs on top of WordPress MU so any spam issues are still, at its core, a WPMU issue.
The WPMU readme.txt has some info on how to counter spammers:
https://trac.mu.wordpress.org/browser/trunk/README.txt (read line 165 and on)
For the Darcy Norman link, use WPMUTutorials’ variation for BuddyPress:
Also, for your suggestion on moderating signups, WPMUTutorials also has an article on that:
Read the last comment in that post for info on modifying the article’s instructions for BuddyPress.
You might also want to check out SI Captcha:
The beta version has support for BP as well.
Hope that helps in some way!