Everything Is Miscellaneous, by David Weinberger, 2007 (read 2007)
The title sounds like a joke. "Um, put it under F, for file." But the sub-title, The Power of the New Digital Disorder, puts everything in perspective.
Weinberger systematically describes what he calls the three orders of order, the three ways we humans try to keep things sorted. One is arranging physical objects. The second is arranging one-to-one records of objects, like index cards or file folders. The third is to assign tags or keywords to each object (or idea) but leave them loose without arranging them in any way. And it's the third method that gives digital disorder its power.
Miscellaneous reviews the history of alphabetization, the rise of the early encyclopedists, and the Dewey Decimal System. Weinberger draws an instructive comparison between two well-known photo archives, the paper-filed second-order Bettman Archive and the digitally-tagged third-order Corbis Archive.
If you've wondered what digital tagging is all about, here it is.