This tool only seems to work with files. If I examine my own computer use, I see that I don't use files directly anymore. I edit/manage my photos with Aperture, it doesn't matter to me where they are on my hard drive. I manage and play music in iTunes. I'm happy to let it manage the files, because it's a pita to manage a huge music collection by hand. At work I work with Visual Studio and TFS. Yes, I know what my local working folder is, but I don't have to. Whenever I need to edit a document, the fastest way is to open the word processor and open the file via 'Recent Files'. I rarely need to access the files directly or know where they are.
Besides, I don't want the same format on every device. I don't want a 16MB RAW file on my phone, just because I used the same file in Aperture.
Just because I made a document in Word, doesn't mean I want to have the word document on-the-go, when I just have it there for review and an e-reader optimized version is a lot easier.
I rip my cd's in Apple Lossless or iTunes Plus, because that's how it works and I have lots of hdd space. On my netbook, those files are way too big and everybody knows how much of a pita iTunes on a slow Windows box is. At the moment, I have to manually manage a shadow library with 160 kbit mp3's.
And what about contacts? Bookmarks? I don't want those things as files in a certain format, I want to use the appropriate program to access that information.
Wouldn't it be nice to have a library with source files on DropBox Online and a set of filters to generate the right libraries, protocols and formats for use on your devices?