Healthcare is awash in data. A typical hospital generates 50 petabytes - a million gigabytes - of it each year. But what are we measuring, exactly? Where does that data go? Why is most of it wasted? And does what we're measuring really need to be measured? Wendy and Matt talk about modern medicine's growing obsession with big data, how data drives social behavior, and the questions we all must ask before consenting to more data gathering - from our patients or ourselves.