Nobody believes AT&T’s $48 billion shot at buying DirecTV will be the last attempt by the nation’s communications leviathans to get even bigger. Verizon will inevitably try to bulk up in response to Comcast’s $45 billion grab for Time Warner Cable. Sprint, the No. 3 wireless carrier, is lusting for No. 4 T-Mobile.

Each of these deals, of course, is justified by the drive to compete. Yet three decades after the United States dismembered its telecom monopoly, the melee of mergers is reshaping the backbone of the information age — including telephone, cable television and broadband Internet — into an oligopoly where competitors are in short supply.

“They say they have to become larger because the other one is becoming larger,” said Eli Noam of Columbia University, who directs its Institute for Tele-Information. “What is the limiting principle?”

Indeed. And it isn’t just the distributors: “Content” providers like Amazon, Google and Facebook dominate their markets as well.