Example 4.7 The social networking website, Facebook, began operation in 2004 and had a million users by the end of the year. By early 2011, with over EGG million users, Facebook became the world's second most visited website {after Google). A strong positive network externality was central to Facebook's success. To understand this, just ask yourself why you would join Facebook rather than some other social networking site. You would join because so many other people have joined. The more friends that also joined, the more useful the site becomes for you as a way to share news and other information with friends. Conversely, if you are the only one of your social circle who does not use Facebook, you may find yourself out of the loop with respect to news and upcoming events. With more members, there are more people to meet or reconnect with, a bigger audience for your photos and opinions, and generally, a larger variety of content for you to enjoy. In Table 4.5IE', you can see that as the number of Facebook users has grown, the time the average user spent on the site grew as well. Table 4.5 Facebook Users Year Facebook Users (Millions) Hours per User per Month 2004 1 2005 5.5 2006 12