"The year 2000 also happened to be when federal regulators approved a merger between two tech titans that some now say should be instructive for the Justice Department and the Federal Communications Commission, as the two agencies review a current-day proposal by Comcast to acquire Time Warner Cable. The 2000 merger, known as AT&T-MediaOne, offers a precedent. But it also raises further questions about certain rules we've established to ensure competition in the marketplace."