Earlier quoted context omitted.
IPFS can't give you the least-seeded files. It can't give you any files, you have to manually pin the set you want, and you pin all of it, and it won't automatically change. It's not very convenient for archival, whereas the system I'm talking about would be (in my opinion, anyway).
(How) would you filter junk?
This is basically an opportunistic, distributed filesystem that's designed to work with high latency links. Only the tracker can write to its nodes, but anyone can read.