where do uploads to buddypress get stored?

Hey. I'm building my BuddyPress network. However, i'm concerned about lots of uploaded media filling up the database.

I notice that it doesn't seem to show up in my Media Library when I use the BuddyPress Activity+ plugin from WPMUDEV, but * does * when I use rtMedia Pro.

How can I manage this?

Where does it go in the case of BP-Activity+, and how can I manage the uploads from rtMedia Pro if I want to go that way?

I imagine that when I have many users, all uploading content (as they've been doing with Facebook) that it could get pretty big pretty quickly.

How does this function?

Also, is there a way to store the media uploaded on an outside site? Something to reduce on the load? Or do these things even matter?