I think some file systems at least aren't as incompatible with this idea as one would think. In linux (all fs?) one has hard-links, which pretty much decouple

I think some file systems at least aren't as incompatible with this idea as one would think. In linux (all fs?) one has hard-links, which pretty much decouple the file from its location. And from what I remember in earlier FATs, you have different mechanisms for file management and location management (File Allocation Tables for file management, and special directory files over it). As to why there is no application to take advantage of it... maybe because it requires too much mind-bending. Most people stay as far away as possible from hard links. When you delete a file you want it deleted, not just "not here anymore".