Scroll down on the page and look at the cloud-display.
(if gone, try the Widgetopia screenshot)
I think the future of metadata is not how it lets you retrieve things (which is all well and good) but how it lets you perceive things.
For some time I’ve thought tag clouds like those on del.ico.us & flickr’s are far more useful for understanding the mind of a group, as opposed to retrieval (I think they are stinky at directed search, and just okay at undirected). This particular instance is a good example of telling you about the nature of the book. Not just the prominence of “people” over “users” but the size of the word “should” which I first thought to be useless– it is, if you want to know what the book about, but not so much if you want to understand the tone of the book.
It would be interesting to compare, say, Jakob Nielson’s first and last book to see how his language changes as he goes from scholarly to didactic.
Now image if it wasn’t just the author’s language, but the tags as well– you could compare intent with effect.