Folder-nesting is essentially set-inclusion, sometimes termed an 'isa-hierarchy'; a related idea is that of 'inheritance'.
Given an isa-hierarchy (a tree structure), a language to describe it is most simply effected by labelling the branches in order:
"Dropbox/mydata/camping/camping-list.docx"where the language syntax is pretty much isomorphic to the semantic structure.
It was a small shock when Gmail introduced arbitrary labels to replace folders. The semantic space became somewhat more complex, as the set of all subsets of a collection of labels constitutes a lattice.
A simple Google search on keywords is not dissimilar to a search on labels (plus a fancy ordering relation wherein lies the magic).
Then came Google Photos, where all those carefully-named folders on your hard-drive ('My-Pictures/Holiday-in-the-Dordogne-July-2014') vanished, and Google used metadata and AI scene recognition to organise your photos along many dimensions: people, places, things-in-the-picture, etc.
In real life and in ordinary conversation, people do not restrict themselves to labels to refer to things.
"That famous joke by that dead middle class comedian"doesn't get a useful hit from Google today, although many British people might hazard a guess.
As Google augments its bottom-up, neural-net phrase-recognisers with stable and ubiquitous semantic/pragmatic models, the clunky, manual world of the folder hierarchy will finally be put to rest.
Google tried to bring a version of search to the personal hard-drive once before, but it never really took off: too much noise and not enough signal in the results.
But next time around?
Folders: archaic, inflexible, labour-intensive .. and doomed.