Facebook, through its platform offering, ushered in a wave of website application innovation. For large web and mobile technology ventures, it is no longer enough to focus just on user adoption—developer adoption of a platform has become just as important. No amount of users can substitute for a cadre of independent developers. The most successful companies, such as Twitter and Facebook, now prioritize their API users the same way first generation web companies catered to unique website visitors. By supplying a platform for third-party developers to build upon, companies can harness outside creativity to drive growth on their platforms. API adoption has led to follow-on innovation and, in many cases, development of critical features that redefine the underlying platform.