In a world of social networks, mobile computing, and billions of smart sensors, we are now awash in data. New tools to harness data are powering self-driving cars, lifecasting athletes, and real-time flu-tracking. For businesses, big data poses new challenges, and demands new kinds of leadership. But for those who can master it, data will offer incredible sources of innovation and customer insight, and provide the answers to some of marketing's most vexing questions.