Idea: Something to make off-site backups easier, and more accessible.

Something that works similarly to bittorrent.
You get credits of some sort for hosting portions (which are encrypted) of people's backups, which you can then "spend" on "seeding" your backup.
The more copies of an encrypted portion there are, the more it will "cost"; so you seed more of other people's portions to "pay" for it.

Feasible idea? Has it already been done? Idk.