This article is very interesting. The iTunes example in particular shows that these measures have to be transparent or they won't work very well. I think this

This article is very interesting. The iTunes example in particular shows that these measures have to be transparent or they won't work very well. I think this was very much Microsoft's vision for Livemesh; they were thinking about desktop apps running data across the cloud. There's a real potential for dropbox if they could somehow hook into a variety of web apps and provide a common back end. The problem at the moment is that if you assume much of the app work people do will move into the browser, you're losing the common file base. You have several app-specific silos across the web.