BuddyPress on Multisite

BuddyPress sits on top of an entire WordPress
installation, regardless of configuration. That means on single-site,
multi-site, or multi-network installations, BuddyPress only has 1 set
of data tables. As a result, you only have 1 set of Groups, Activity,
Private Messages, Profiles, and Friends, even if you have 1 site/1
network, 100 sites/1 network, 100 sites per network/100 networks.