I was thinking this morning that this is about my 20th aniversary of experimenting with hypertext technologies (which I view as any chunks of information with typed links): using the Grapher (DAGs) on my Xerox Lisp Machine in the early 1980s to visualize typed links between data; a commercial Smalltalk class library to do the same thing a few years later; Owl Guide hypertext authoring tool on the Mac; ordering and reading the Ted Nelson's Xanadu manefesto document; using a text-based browser to explore physics documents at CERN in the very early 1990s (my first exposure to HTTP protocol and HTML - thanks to Karl Weibe for that!), etc.
In earlier history, some wealthy people had their own personal libraries to store and organize knowledge. Now the tools are better and usually support close to free access to information.
As good as graphical user interfaces are for browsing the web, examining links between data sources, etc., I still think that the "killer application" for knowledge management will have a simple (mostly) text interface that uses natural language understanding and (in a semantic web sort of way) be able to search on content based on meaning.
As an aside: my top priority research project that I am scheduling about half my time for in December and early next year is to add "RDF generation from plain text" to my KBtextmaster system. I will post a link when I have a white paper ready on how I plan on doing this.