Exxon Mobil has spent $230 million in the past 30 years underwriting PBS’ “Masterpiece Theatre”. No more. “The company wants to target its messages in the environmental realms that more closely align with its businesses. It’s a message public broadcasting executives are hearing frequently these days.” Many companies “are saying they simply have no extra pocket change in the down economy for image messages – the only thing that public television’s strict rules allow – that aren’t directly tied to getting consumers to buy a product. That puts PBS, and local stations that air its programming, in an increasingly difficult situation.”