Must a MU BuddyPress Install be 'Network Activate'?

I have on http://www.networkit.com the latest WP install, MU enabled + BuddyPress version 1.2.6

My question is: Must a MU BuddyPress Install be 'Network Activate' in such a configuration? Is it possible to activate BP on just some of the blogs and not on others?

Much thanks.