I like this concept. There is another company that has been doing this for a few years now, but there execution wasn’t very good. I could never get it working on my network and from what I’ve read it was very slow to upload/download. http://www.symform.com/
I would really like a software that lets you create your own private cloud for P2P synced backups. You could take all the computers in your company for example and backup amoungst them using free space on everyone’s drives.