For more than 60 years, TV stations have broadcast news, sports and entertainment for free and made their money by showing commercials. That might not work much longer.

The business model is unraveling at ABC, CBS, NBC and Fox and the local stations that carry the networks' programming. Cable TV and the Web have fractured the audience for free TV and siphoned its ad dollars. The recession has squeezed advertising further, forcing broadcasters to accelerate their push for new revenue to pay for programming.