Platform businesses reshape industries by dramatically improving the economics of integration and service delivery. You can participate in a platform economy by exposing capabilities via APIs and adopting partners' platforms. But to lead, digital business leaders must build services that customers and suppliers embed into their operations. We interviewed 33 platform businesses, including Dropbox, General Electric, PayPal, and SupplyOn, to find out how. The answer? Start with a real customer problem, not ecosystem envy.