Therefore “Open In”: a menu that copies a file from Location A to Location B, getting from one document to two documents, now available in two different locations. And I would argue that the second most complicated aspect of managing documents is: figuring out the “right” version of a file.
Viticci is right, of course, that’s something I hadn’t considered. The duplication effect would be horrible, so perhaps a better solution is something more akin to “send this here file to that there app”. Or just a button that reads “Send to…” or “Move to…” depending on which wording Apple likes better (my vote is Send to).
That would essentially allow you to relocate a file from one silo to another instead of duplicating it. The trouble here for users would simply be remembering where they sent the file, but that’s still less frustrating for average users than seeing the actual file system as you do in Finder.