Whether you think Facebook is a formidable business, a great place to find old school chums, or a terrific waste of time, it is ultimately just a moment in the long evolution of the internet. And its moment will pass.

The internet has a way of breaking established orders. Time was, people who wanted to congregate fished start-up disks from their junk mail, got dial-up modems, and went to America Online. Then came the world wide web, and it was suddenly cool to have one’s own website. AOL was toast. Then a smart fellow named...