Re: Conservative “unbreakable” use of buddypress
As you’ve surmised, if you want to share files or use an image gallery, you’re going to have to find a 3rd-party plugin that provides those features. As to how well they will work with WPMU and BuddyPress, you’ll have to try to find out.
Yes, a plugin installed to /mu-plugins/ will automatically be used on every blog, and one installed to /plugins/ will be available to every blog to use.
What tends to break BuddyPress? Er. Let’s find out! 
