I have a design for a system where you can "donate" your disk space to a provider. Basically, you run the client, you say you want to make 1TB available to archive.org, and their server can push the rarest content to your computer.

It's based on torrents, and you can easily make a content delivery system on top of this (so people can fetch data from this network).

I emailed a few archiving teams but nobody seemed interested, so I never made it.