Billionaire brothers Charles and David Koch are quite entrepreneurial in their attempts to influence public policy in their favor. They don't just donate to a few like-minded politicians: They have long funded libertarian think tanks like the Cato Institute. They helped fund the Tea Party movement. In the 2012 election, they funded groups like Americans for Prosperity to air campaign ads attacking Barack Obama during the last presidential campaign. While their reported interest in buying the Tribune Company's eight newspapers, which includes the Chicago Tribune and the Los Angeles Times, has stirred up fears from journalists and activists in those cities that the Koch brothers would extend their influence into media, their limited involvement with the media has already yielded success.

David Koch is on the board of New York PBS station WNET -- and his status as a mega-donor -- led the station to air a rebuttal to a program that used his apartment building as a symbol for the gap between rich and poor, and to refuse to air a documentary about the Kochs' role in the 2010 governor's race in Wisconsin, The New Yorker's Jane Mayer reports. In the end, it didn't matter for WNET. Koch quit the board and decided against a major donation.

The government funds just 12 percent of PBS's budget, which means it and its member stations are dependent on charitable contributions for the rest. That means that PBS programming that argues that the middle class ("Viewers Like You") should pay lower tax rates than the very rich (like David Koch and the rest of the donors who get thanked by name) is targeting the people who pay to keep that programming on the air. And that's kind of what happened when New York's WNET and Boston's WGBH, whose boards Koch sits on, decided to air a documentary called Park Avenue: Money, Power and the American Dream on November 12. It used the residents of the New York City building at 740 Park Avenue to tell the story of income inequality. The Kochs are residents. As the content of the film became clear, the president of WNET, Neal Shapiro, became nervous. He phoned David Koch in advance. He invited Koch to sit on a panel to discuss the film after it aired. Koch doesn't make many public appearances, so he offered a written response. WNET aired a statement from Koch Industries after the film aired, which Mayer describes as an unprecedented move "like appending Letters to the Editor to a front-page article."

The controversy pushed self-censorship downstream. WNET said it had been blindsided by Independent Television Service, which funded the Park Avenue film and many other documentaries aired by PBS stations. And so a few months after that documentary aired, ITVS decided not to fund Citizen Koch, a documentary about politics after the Supreme Court's Citizens United decision that focused on the Kochs' funding of Wisconsin Gov. Scott Walker.

In the end, the self-censorship didn't save WNET's funding. David Koch quit the board, and decided against a big gift to the station. "It was going to be a seven-figure donation—maybe more," a source told Mayer. How would editors at Tribune newspapers take in these considerations if the Kochs were directly responsible for their paychecks? It's a question the Koch brothers are probably asking, too. The Kochs are keenly aware of the efficacy of their public advocacy, conducting a review of what went wrong with their ads in the 2012 elections. While Koch might have quit the WNET board, just being a member had undeniable results. Being an owner of eight newspapers could be irresistible.