A year ago this week, when he completed the purchase of Twitter for $44bn, Elon Musk tweeted “the bird is freed”. Billionaires like nothing more than casting themselves as popular liberators, but the acquisition fitted the pattern of his ever-expanding empire. Musk has colonised areas of the economy from which public funding and regulation have been in retreat. His carmaker, Tesla, is shaping the future of transport; SpaceX, meanwhile, has in many ways replaced Nasa on the final frontier (so far this year it has launched 75 spacecraft). Musk told himself and the world that he had acquired Twitter (now...