Mountain Lion’s New File System:
Folders tend to grow deeper and deeper. As soon as we have more than a handful of notions, or (beware!) more than one hierarchical level of notions, it gets hard for most brains to build a mental model of that information architecture. While it is common to have several hierarchy levels in applications and file systems, they actually don’t work very well. We are just not smart enough to deal with notional pyramids. Trying to picture notional systems with several levels is like thinking three moves ahead in chess. Everybody believes that they can, but only a few skilled people really can do it. If you doubt this, prove me wrong by telling me what is in each file menu in your browser…
A well-considered essay on the non-recursive design of folders in iCloud, how people think about organizing documents, the emotions of organizing documents, and how it comes together in an app like iCloud. Great reading.