Known Space makes it possible for websearches to return documents ordered by their likely relevance to the user's home documents. Also, with Known Space there can be two kinds of web searches: searches within the home and searches within the web as a whole. Automating the webmapping process would make it possible for your computer to tell you exactly what you're interested in on an ongoing basis. Not only is that useful information for your computer to have to better serve you in future, but it's useful information for you to have too. Further, this same idea can be extended to any database. If in a traditional relational database of car parts the query engine keeps track of the kinds of queries each user poses, it can tailor its responses to each user. Such a query engine would have a much better chance of satisfying each user, no matter how garbled their present request.
The other main idea behind Known Space is that of laying out multi-dimensional information in a two-dimensional map; and that too works for many other information management tasks: searching the Yellow Pages, reading mail, reading news, deciding what movies to watch or music to listen to. Had we such a system handling our mail for instance, then when a new message comes in we would have a rough idea what it's about at a glance. Such a map would be even more useful for news.
Known Space need not stay a web browser interface; it could grow into an semi-autonomous interface to all the world's data--including your computer's files, your mail and news, and any odds and ends your ferrets pick up that they judge may be relevant to you. The world then becomes a universe of documents. Your ferrets roam that world looking for things that you might find interesting and either point you to them or copy them for you if they are considered too important and too transient to miss. Besides mail, news, and local files, those documents could be anything: html files, ftpable files, gopher files, files of who was logged on to a particular machine in China at 3am on Friday, electronic news articles (which will certainly disappear unless a ferret says ``Hey, we need to copy this''), and processes that mysteriously appear on your machine at 3am from an unknown machine in China. Finally, you might want to make your view of reality--for that is effectively what this is--sharable (or even salable).
When your Known Space gets really large, you'll probably need a small and separate working set of documents and pointers--pointing perhaps even to documents already on your computer (but hard to find or deep inside site clusters). Then this working set could grow large enough to need its own map and so on.
Of course, all of this is a fantasy today, since it depends on building ferrets so smart than they do a tolerable job of reading your mind and thus anticipating whether you're likely to find a particular document interesting enough to keep around.