Facebook CEO Mark Zuckerberg officially launched FWD.us, his immigration reform group made up of such Silicon Valley luminaries as Marissa Mayer, Eric Schmidt, Bill Gates, and Steve Ballmer. However, the group's impressive list of members just got a little shorter — according to Reuters, SpaceX and Tesla Motors founder Elon Musk has officially left the group after it funded advertisements for senators who support an oil pipeline and oil drilling in Alaska. The ads themselves were focused more on the senators' general policies and positions rather than immigration specifically, including support for the Keystone XL oil pipeline. There was a quick backlash from a number of progressive or environmental-focused organizations like MoveOn.org and Sierra Club, which pulled their advertising from Facebook in response. While Musk declined to elaborate on his reasons for leaving Zuckerberg's immigration group, his all-electric Tesla Motors is one of the best-known green companies around.