Last night, before sleep, I thought of this:
The new sharing system should be something as simple as a distributed, syncronized filesystem.
This new filesync should sync the files on a certain directory; for all it's nodes (users). It should use rsync or something similar so it could send the changes only and calculate hashes to compare the files.
It should hold the list of nodes or, users, in the same dir; so everybody has the list.
There would be one master source and, when validated, the other nodes could become masters (multiple masters). Also, a node could "fork" the dir and add/change the files.
Everytime the master updates the share, you would have to authorize the changes.
This would let us share files easier and let us stop looking, eternally, for the updated torrent file or the rapidshare links to episodes of house! ;)
If done right, this could serve as a very cool replicated filesystem over Internet. Not only let us share files but, for example, share a whole server (google style; small spec nodes but millions of them!) in our machines. You could decide to "sync" some cool website you like and help them with the hosting.
Besides, we could add really cool features like encryption and stuff. Cool idea, huh?