AP: Greenpeace said about 500,000 Facebook users have urged the world’s largest social network to abandon plans to buy electricity from a coal-based energy company for its new data center in the U.S. Greenpeace Executive Director Kumi Naidoo sent a letter Wednesday to Facebook founder Mark Zuckerberg warning that the company risked its reputation and financial health if it ignored the environmental impacts of its actions. “Facebook is really out of step with the trend” among …