In October 2006, Mr. Obama, who had been elected to the Senate from Illinois two years earlier, published his second book, “The Audacity of Hope: Thoughts on Reclaiming the American Dream.” He wrote of visiting Google headquarters in Mountain View, Calif., where, among other things, he saw a map of the world with lights showing where Google searches were going on. Swaths of Africa and South Asia were dark. But so were portions of the United States, he wrote, where “thick cords of light dissolved into a few discrete strands.”