Stockshot images of Facebook's headquarters in Menlo Park, California, as Facebook reports its profit doubled in the recently ended quarter with digital advertising surging, but warned of cooler growth in the months ahead. Profit jumped $10.4 billion on revenue of $29 billion, with the number of people using the social network monthly climbing to 2.9 billion, Facebook says in a second quarter update that sparked an after-hours selloff. STOCKSHOTS of Facebook's headquarters in Menlo Park, California