I've finally started writing one of the ideas I've had mulling around in my noggin for years.
What does it do?
It allows people to back up files securely and privately across a network of peers. Peers may specify the max amount of storage they will allow. All the peers receive and store are pre-encrypted chunks of a file. On receipt they encrypt it a second time with a random-generated key and send the key back to the file's source.
Any peer can retrieve any file from the network with:
1) The file's generated uuid
2) The chunk's host key
3) The origin's key
My current goal is to build a functional alpha build and test it with several people. I whipped up a utility that encrypts files accordingly, and I'm currently working on writing the tracker software.
It seems like a neat idea. I feel more peer to peer applications are going to start emerging and though this idea might not stick, hopefully lessons may be learned as I try piecing this together. :)