I think hierarchies are one of the most common ways to organize data and most systems in this world are organized hierarchically. Governments, socioeconomic systems, taxonomies, literature, organized religion, and nature, are all often organized hierarchically. Humans seem to think in hierarchies better than in many other systems of organization. Sure, search is great, but even sites like Newegg and Amazon prominently display hierarchies to organize data, and I appreciate it. I don't think hierarchal file systems are dead at all. I think they are a very good way of organizing most file system data, and that search can be of utility even in a hierarchal file system.
Every computer system that uses tagging is a counterexample. We humans think in tagging as often as we think in hierarchies, but I agree that we tend to think of hierarchies as more well-defined and organized. This tendency can be incorrect.
I think it boils down to this: for hierarchical data, use hierarchies. I believe that files on a modern personal computer will almost certainly not be hierarchical, so it's not ideal to store them hierarchically. Videos, for example, may be movies, tv shows, screencasts, music videos, etc. Videos may also be standard definition, 720p, 1080p, etc. It's difficult to say, for example, which attribute should be the root directory for your videos, since it's reasonable to want to browse by many different attributes. A hierarchy does not apply to videos, but attributes could easily be represented by tags.
I agree. Maybe we need a hierarchical system that is dynamic. We need to organize information and in the real world we are constrained, but with computers we are not.
E.g if I need to organize my books, I could move it only to a given position, not another one, I could add labels to my books like "history", or "Initials of the author", but I could only group one way, like all my science papers on one place, if I want to group all the books that talk about sex, or crime, I will have to destroy the other group.
With computers you could create multiple directories trees with links instead of data, so I don't need to multiply the data each new tree. The tech is there(inodes).
Imagine if you study countries according to their population, so you create a hierarchy "most populated", "less populated", "no populated at all", then inside most populated you have "the most populated", "the less populated", and so on.
Then you could have another directory according to the extension in squared kilometers. Another according to their capital coordinates, and so on.
