How hard would it be to go a week without Google? Or, to up the ante, without Facebook, Amazon, Skype, Twitter, Apple, eBay and Google? It wouldn't be impossible, but for even a moderate Internet user, it would be a real pain. Forgoing Google and Amazon is just inconvenient; forgoing Facebook or Twitter means giving up whole categories of activity. For most of us, avoiding the Internet's dominant firms would be a lot harder than bypassing Starbucks, Wal-Mart or other companies that dominate some corner of what was once called the real world.

The...