Why is Oprah Winfrey jumping from broadcasting to cable? For the same reason that the largest cable company, Comcast, is bidding to buy NBC/Universal. Cable networks are one of the few traditional media enterprises that are growing. The audience for broadcast television is shrinking. Cable generates two income streams, advertising and subscriptions; broadcasting relies solely on ads. Oprah is jumping off the listing ship and onto the rocket. Similarly, Comcast’s primary motivation is not to own the network, or the stations, or the movie studio. They lust for thriving cable channels like CNBC and Bravo and the USA Network. Owners of cable wires like Comcast are racing the telephone companies to own content so they don’t become marginalized into dumb pipes. In Mike Nichols’s “The Graduate,” Mr. Robinson advised Benjamin that “plastics” should be his future. Oprah, like Comcast, is saying that cable networks are the future.