I've been wondering about this for that use case myself: https://ipfs.io/
I think GlusterFS (battle-proof, but file-wise and assumes an administrator with access to everything) assumes or infinit.sh (robust ACL, but young, not open-source) better addresses those use-cases.
Also, when adding files yourself, those files become pinned by the default. Getting files won't pin automatically however. You have some more information about pinning here: https://github.com/ipfs/examples/tree/master/examples/pinnin...