Until recently, Facebook had an "it's complicated" relationship with coal; an April 2011 Greenpeace report found that 53.2 percent of the company's electricity use was coal-generated. Now, the company is pledging to move away from dirty fuel and work towards powering its operations, including energy-suck data centers, using renewable energy. And they're helping to spread the word to others.
The move from coal to renewables won't be as slow or rocky as the move from Facebook to Google+, but it's not going to be instantaneous. Still, the company has committed to foregrounding "access to clean and renewable energy" when considering data center sites (they've built one already), and will also use its considerable resources to help coordinate and mobilize energy-saving programs.
This is a win for Greenpeace, which has been needling the company for years about its coal dependence, including an "Unfriend Facebook" campaign that mobilized 700,000 supporters. (People are always inclined to be irritated with Facebook for basically anything, which can't have hurt.) Facebook and Greenpeace will be working together to encourage renewables use and energy conservation, including encouraging utilities to invest in renewables.