BuddyPress.org

Here is my understanding (after looking a the BP code) :

The avatar link is not in the DB. It’s just a path + the user ID as last directory.

On my installation it’s /www/wp-content/blogs.dir/3/files/avatars/[ID of the user]

My personnal issue is that when the user sign-in, the directory is not created at the right place, so user cannot see their avatar then.