It occurred to me last night that I want to do offsite backups of my personal data, and would be willing to donate hard drive space to the cause. So I was thinking I'd write a p2p system where anybody could join and store whatever they wanted (heavily encrypted and all that) as long as they donated drive space to the cause for others to use. I was planning my design when I thought maybe somebody had already done this? Ring a bell?
If not maybe I'll start the project.