BuddyPress.org

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:

http://wpmututorials.com/how-to/spam-blogs-and-buddypress/

—

Also, for your suggestion on moderating signups, WPMUTutorials also has an article on that:

http://wpmututorials.com/hacks/how-to-moderate-signups/

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:

https://buddypress.org/forums/topic/si-captcha-for-wpmu-and-buddypress

The beta version has support for BP as well.

Hope that helps in some way!