Today's mobile device is the new personal computer. The average smart phone is as powerful as a high-end Mac or PC of less than a decade ago. And as billions of people worldwide rely on these ultra-compact machines for more and more tasks, the mobile device might qualify as humankind's primary tool. We are only just beginning to fathom what this reality implies for business, culture, and society. Our phones can now track our movements though the physical world. They can record our social interactions, store our personal histories, keep tabs on our likes and dislikes, and track our Internet content consumption, app usage, and purchasing behavior.