ATLANTA—After deciding to disable his Facebook account in an effort to increase productivity, Chad Allen announced in a Facebook update Thursday that he was now "off the grid." "I'm dropping off the radar for a while," wrote Allen, 36, who lives in a two-story house with running water, electricity, regular garbage pickup, wireless Internet access, and high-definition satellite television service. "If you need something, text me." Allen has not been heard from since earlier this afternoon, when he confirmed via Twitter that he was "maintaining radio silence" and then checked in to his local coffee shop on Foursquare.