An interesting experiment in pervasive hyperlinking is taking place at GuruNet. (No relation to guru.com) What they make is a small program, sort of like a browser plug-in, that lets you Alt-click on a word in any Windows application (not just browsers) and get information on that word.
Right now, the information is mostly limited to dictionary definitions, but I'm sure down the road the database of hyperlinks and other resources will vastly expand. The app also has a great pedigree, with one of the key investors being Mark Tebbe, who was founder of Lante, and, until his recent departure, was one of my favorite columnists at InfoWorld.
I think there's still more than a few user interface inadequacies to be resolved in the program, but its potential makes it well worth the small download. However, the biggest flaw that I can see in this program is that there is no accommodation for user-supplied links. The best way to tap the potential of a program like this is to allow for the community of users to contribute to its value.My suggestion would be a three-tiered system. At the narrowest, and highest-quality, level, only GuruNet-supplied links would be available upon clicking a word, with all links entered and verified by their staff. Limited, sure, but also more likely to be useful.
At the second level would be a filtered user-supplied directory of links. Perhaps through a cross-licensing with the database of the Open Directory or About.com, or simply through editing links suggested by GuruNet users, a high-quality, high-volume database of links could be added to the program.
At the lowest quality, but with the highest quantity, of links would be a totally open database, either through passing queries to a standard large search engine (AltaVista, HotBot, or maybe a more refined one like Google or Northern Light.)
Of course, this being a software program, plenty of warnings and "Are you sure?"s would have to be added, so that people would realize they were opening up the potential of spam and advertising, etc. I'm assuming that advertising on GuruNet Alt-clicks is already part of their long-term revenue model.