Small Pieces Loosely Joined (Kids' Version) by David Weinberger. Just a little over-done, I think, but the sentiment is nice.

This is a most peculiar thing. The Web is a web because of hyperlinks that connect the pages. But every hyperlink expresses someone's interests and recommendations. If you were to make a map of the Web, showing all the sites and all the links, you would be making a map of things the 500 million people on the Web find interesting.

That's a lot different than a map of the real world that shows where the mountains are and where the oceans end and land begins. The real world map shows what we humans have been given to work with. The Web shows what we have chosen to care about.

And that's exactly what's so special about the Web place. It is made not out of mountains, oceans, deserts and forests. It is made out of humans caring about things together.