Says The Guardian:
The funding cut – just $15,000 a year – is small beer for the institute, which has a multi-million dollar turnover, largely from a single anonymous donor. But it is a blow to the standing of the think tank and to the leading role it plays as an advocate of climate change skepticism.The pullout comes after leaked documents revealed that Heartland Institute received funds from various corporations, including GM, that are publicly committed to "social responsibility."
Here is one of the leaked documents that shows Heartland Institute's 2012 fundraising plan. The rest of the leaked documents can be found here.