I'm specifically not suggesting that systems necessarily need a file metaphor. I'm concerned about what happens when every app has its own idiosyncratic UX patt

I'm specifically not suggesting that systems necessarily need a file metaphor. I'm concerned about what happens when every app has its own idiosyncratic UX pattern for saving/committing your work. I know people who have lost work in web apps (e.g. issue tracking systems) because it's not obvious when their changes are actually committed as opposed to sitting in memory in their browser, and people who have been bitten by weird interactions between auto-save and undo in IDEs.