There isn't just one social graph, there are many. LinkedIn maintains your professional contacts, while Facebook has friends and family (and yes, often many professional). Twitter has some mix, as well, perhaps with a different filter. Aggregators take these disparate contacts and bring them into one place. A new service uses several APIs to merge them and give tools to better understand and utilize your network of contacts.
More and more consumers are using a second device (usually a mobile device such as a smartphone or tablet) while watching television. Many consumers are using their "second-screen" to update their Facebook status, post on Twitter, chat with friends or engage in other online social activities.