You could build a Dropbox clone where users have the option of contributing storage to get rewarded with real currency. Why would anyone want to use the decentralized version instead, both as a user and as a contributor of storage?
The decentralized version is going to be much harder to get right for the developers, and why should the users believe that the technology is trustworthy? I just don't see the advantage, but I would be truly interested in hearing what I may be missing.