Facebook CEO Mark Zuckerberg revealed today that the company now has over 1 billion monthly active users on mobile devices. Zuckerberg cited the statistic during an investor call to discuss the just-announced acquisition of virtual reality firm Oculus VR. In the fourth quarter of 2013, Facebook had 945 million active mobile users out of a total of 1.23 billion users. Photo credit:_Leon Neal/AFP/Getty Images