In an extensive and thorough dissection of the O'Reilly-Olbermann feud, Howard Kurtz reveals the cable news duel has gone to the tops of both personalities' parent companies: Rupert Murdoch at News Corp. and Jeff Immelt at GE.

But the feud goes beyond Olbermann naming O'Reilly 'Worst Person,' or O'Reilly criticizing NBC for 'being in the tank for Obama.' Recently, O'Reilly has been going after Immelt for GE's history of doing business with Iran. The back-and-forth really heated up last summer when a Daily Kos blogger "made a scene" at O'Reilly's home.

It was then, Kurtz writes, that "back-channel discussions" involving Fox News Chairman Roger Ailes and NBC's Jeff Zucker began.

Ailes called Zucker on his cellphone last summer. According to sources familiar with the conversation, Ailes warned that if Olbermann didn't stop such attacks against Fox, he would unleash O'Reilly against NBC and would use the New York Post as well.

Fox News spokesman Brian Lewis said Ailes never offered a "quid pro quo." GE spokesman Gary Sheffer tells a different story. He told Kurtz, News Corp. execs "tell us if the attacks on O'Reilly end, the attacks on GE will end. They've had conversations with our news executives saying, 'If you stop, we'll stop.'"