I recently installed buddypress on my website the first in my signature list. Within hours I had over 250 spam registrations this was becoming a problem because I was already using the G.A.S.P Plugin for Wordpress http://wordpress.org/extend/plugins/growmap-anti-spambot-plugin/ this does a great job combating comment spam by placing a simple checkbox under the comment form and does not annoy visitors by making the fill in a captcha question. There will still be a few human spammers that may slip through but it works much better than akismet. But it was not enough in combating registration spam so I have installed the SI CAPTCHA Anti-Spam plugin http://wordpress.org/extend/plugins/si-captcha-for-wordpress/ and set it only to show on the registration form this will not annoy visitors making comments or users that want to login but will stop spam registrations. I hope this helps you with your buddypress installation. Has anyone else got any tips to block spammers registering on your buddypress site please share them below.