As one of the developers/founders of Openomy (
http://www.openomy.com), I'm keenly interested in this.
Our goal is to provide a place where people can store and access all their online files. We want to be the Online File System. We're heading to the "cloud" already and it's becoming increasingly difficult for us to manage our own files. My photos are locked in Flickr, my docs in Zoho, etc.
We want to break down the "data silos" and provide a single interface to all your "cloud storage" as well as provide a single API for developers to code against to access user's data in meaningful and interesting ways.
We're taking a multi-pronged approach to this. One prong (currently launched) is to allow you to upload your files through our API or our web interface and we'll store it (using Amazon's S3 for reliability and scalability). You can access the files and their metadata through the UI or through the API. You can tag them, share them, make them public, etc.
Our next step is to provide many backing-stores. That is, import your files from Flickr/Zoho, etc. We'll keep things sync'd up, so that Openomy becomes your Online File System; storing the metadata of everything you do online. Then, the UI becomes the equivalent of Windows Explorer or Finder, and the API becomes the equivalent of the single file system API provided to you as a desktop developer.
We think it's going to be, at the very least, extremely fun to build. :)