I haven't seen a chart that shows the breakdown of how much viewer support versus government support versus corporate support for CPB, but do know that more and more CPB has corporate sponsorship of programs, including Walmart. And that corporate sponsorship affects what programs PBS or NPR will air-nothing that might offend and cut off the tap.
The board also has veered to the right- Cheryl Halpern thnks it's okay for board members to intervene to censor content -
http://www.alternet.org/mediaculture/18831/There used to be an argument from the right that the taxpayer shouldn't be funding public broadcasting (I remember a crisis public broadcasting some time back when it appeared it would end and the public rallied). Selfish, but because at the time it was the only major alternative to the wasteland, it seemed worth fighting for. And perhaps it's time to address whether paying for public broadcasting still serves its purpose.
But when you have a man heading it who does not watch tv, who would prefer to read People magazine over watching Jim Leher news, who was for media monopolies in the same market, who didn't believe in meetings for the public because they are only exercises in "foot-stomping" and one of his fellow board members would act as a censor for content, not sending them one more thin dime is NOT an unreasonable action to take.