If I say "Book" and "42", what comes to your mind? Some "Hitchhiking" perhaps?
What with "Umbrella" and "Film"? Any film titles coming to mind?
Add "Nanny", "Flying"... would that be "Mary Poppins"?
See? Your brain is quick and naturally wired to intercept iffy tags!
Nevertheless, I often hear that tree-structures are necessary and that we are hard-wired for tree-structure organising: Hierarchies, folders...
That I would argue, humbly of course, is bogus.
Would "Film > British location > Female lead > Disney > Family > etc." trigger "Mary Poppins!" as promptly?
Nah, didn't think so...
We're naturally inclined to tag imprecisely and freely - and locate any object or subject intercepting those tags. Fast, efficient and without training. And without any quest for standards.
In other words, we need no classic tree structured data sorting. We would be better off without.
And with that goes most of the reason for hierarchies. And with hierarchies goes the command and control nodes named management.
And then departments, and thus marketing as we know it.
And how we build knowledge. And how we learn.
And why not rethink, remake and replace the whole shebang? All of the above.
Yeah, why not? It's only Sunday, enough time to make the world a better place by the end of year :)