Facebook this week is learning some hard lessons about hazards of assuming the mantle of environmentally responsible business practices. Initially, the social networking giant’s first-ever data center build, currently under construction in Prineville, Ore., was hailed as a model of forward-thinking green data center design. Many of the hallmarks are there, including a PUE goal of 1.15, free-cooling, LEED Gold aspirations and buzz surrounding its approach to super-efficient custom severs. The mood was somewhat celebratory and Facebook was showered with goodwill. That is, until someone dropped a four-letter word: coal.