What's missing from this system(and P2P systems in general), is automatic pinning - i.e. the system automatically choses which files to pin on which user, to ensure every file is available on the net.

It's a bit of tricky problem, because people may not like unknown, random files on their pc, and probably, because such algorithm is distributed and will need to resist attacks.

But i think that the payoff is big: what Bitorrent did to popular files, such an algorithm could do to rare files.