Let me tell you a story. Once upon a time a powerful Soviet space physicist, who had defected from his country, with wife and daughter, in order to come to Princeton to develop the physics of quantum gravity, quit. Gone was his goal of building a theory integrating all the forces in nature, knocked out of his head by the World Wide Web. Sasha Migdal began, instead, to write software that makes lifelike models of people because, he said, "I had dreamed since I was a child of a giant network connecting everybody like a single brain. Of course, it's not yet true. But there is a real revolution going on, and I just couldn't resist it."