It took both the telephone and the mobile phone 15 years to amass 100 million users, but Facebook did it in 9 months. We see more and more people becoming connected on online social networks, and it seems our networks are growing exponentially. But the reality is, social networks rarely add to our number of connections. We’ve already met almost all the people we’re connected to on social networks. We’re already connected to these people offline. Social networks simply make the connections visible. For example, we often connect with old school friends, and catch up over a couple of wall posts. But rarely do we continue the conversation once we’ve connected, and over time we forget that the connections exist. In fact, Facebook users often have no interactions with up to 50% of their connections.1 When we study how people are interacting on social networks, we see that most interactions are with a very small subset of the people we’re connected to.