Aren't the successors to Winny (Share and Perfect Dark) like this? I remember one of these programs that I tried out in the past had these hash files that were seeded to others and I had no idea what files I was holding.
You dedicate some space on your hard drive to the program, which then stores chunks of unidentified files there and constantly uploads to other clients - it's true decentralized file storage. It was a cool setup when I tried in back in '08 or so, very cyberpunk with its anonymity and plain-text-on-black UI, and I enjoyed reading the Japanese comments (often with SJIS text art) posted by others on the internal chatstream. In the end I didn't actually use it for anything, but it felt like a futuristic BBS.
It would be interesting to see a global equivalent emerge, maybe built upon bittorent DHTs/magnet links.
