Re: Features for BuddyPress
You could hack together something like Lifestream fairly easily using https://wordpress.org/extend/plugins/bp-external-activity/. There’s no interface for it yet, but the infrastructure is all there.
Jeff Sayre has said that he’ll be releasing his Privacy Component shortly after 1.2.6 is released.
The kind of rich tagging you’re talking about really isn’t possible at the moment. Only when BP’s core components are converted into WordPress content types (like custom post types) will they be able to easily inherit WP’s taxonomy functionality. I’m guessing that will happen in the BP 1.4 range. The good news is that, once it does, tagging/categorization will be totally seamless.