But how did it come to this? First, mobile sensors, social media services, genomic seq uencing, and astronomy are among myriad applications that have generated an explosion of abundant data. For example, smartphones’ suc cess has created the biggest sensor deployment in the world, with millions of users constantly taking pictures and reporting their movements and activities. Social networks from Twitter to Facebook let users continuously generate and share content with friends, producing even more data about what we do and how we interact with each other. Second, storage capacity for the past 30 years has roughly doubled every 14 months, making storing data cheaper than ever. Storage is now so cheap that it’s often better to buy more than try to determine what to delete.