The exit line is getting longer at the U.S. Chamber of Commerce. Recently three big power companies -- Pacific Gas & Electric, PNM and Exelon -- resigned over the chamber's opposition to regulating carbon emissions. Then Nike said it would quit the chamber board for the same reason. Now Apple is canceling its membership. From the letter of Catherine Novelli, Apple's lobbying vice president, to Chamber President Thomas Donohue:

As a company, we are working hard to reduce our own greenhouse gas emissions by relying on renewable energy at our facilities and designing more energy-efficient products for our customers. We have undertaken this unilaterally and without government mandate, because we believe it is the right thing to do. For those companies who cannot or will not do the same, Apple supports regulating greenhouse gas emissions, and it is frustrating to find the Chamber at odds with us in this effort.

The chamber opposes regulating U.S. greenhouse gases unless all major carbon-dioxide-emitting nations promise to reduce their output, too.