BuddyPress.org

interesting:

2) How do spammers find BP communities?
Using Google.
Example: http://www.google.ca/search?hl=en&q=%2B”is+proudly+powered+by+WordPress+and+BuddyPress”; (front page of every BP site on the net)
Example: http://www.google.ca/search?hl=en&q=inurl:%22/community/members/%22+%2Bbuddypress (members page of every BP site on the net)

I have two open test BP installs (one wp_user linked to my blog domain) and changed the standard footer. Not a single spam sign-up (just hashcash installed)