Well in this early stage you would probably just run one or more StorJ nodes, rather than sell space to StorJ. It would kinda work like Bitcoin mining. Bitcoin mining supports the network, and the miners get a percentage of the fees and new coins. For a StorJ node you would get paid the fees for hosting a file or file(s).
I doubt this would replace Dropbox or Megaupload anytime soon, but in its full implementation it would allow you to store your files for very very cheap. Although you are making me think maybe this should be a more of a desktop app. You can make Bitcoin by utilizing a GPU that otherwise might be idle, but instead utilizing your hard drive space that might be empty.
I mean look at the Dropbox model. They charge $99 a year for 100 GB of space. Lets just call it an even $1/GB. Which means if I charged Dropbox prices for a $100 Seagate Barracuda 2TB off Newegg that's fully loaded, I could get <$2,000 a year. That's a better reward that Bitcoin mining. Of course I'm omitting stuff like redundancy, but still there is a huge profit margin in there.
tldr; Back of the napkin calculations make this highly optimistic.
Proof of Storage right? I think this idea can work.
