Social Operating System
= a Social OS is the primary application you use for interacting with your social circles on the Web.
"A subset of social networking sites. In fact, the only application in this category today is Facebook. Before you use your computer, you have to boot your operating system and every interaction with your PC goes through the OS. However instead of interacting directly with the OS, most of the time you interact with applications written on top of the OS. Similarly a Social OS is the primary application you use for interacting with your social circles on the Web. All your social interactions whether they be hanging out, chatting, playing games, watching movies, listening to music, engaging in private gossip or public conversations occurs within this context. This flexibilty is enabled by the fact that the Social OS is a platform that enables one to build various social graph applications on top of it." (http://www.25hoursaday.com/weblog/2007/08/30/TheDifferenceBetweenASocialNetworkSiteASocialGraphApplicationAndASocialOS.aspx)