I've been thinking about SNSs and the way in which boyd and Ellison (2008) anchor their definition to three core characteristics. 1. Individual users or members construct a public or semi-public profile on the site 2. Users/members create and list connections with others (friends, followers or buddies) 3.Users/members traverse the site through their own and others’ friendlists. These characteristics are shared with other environments which may not focus on friendship quite so explicitly (Blogger and similar applications come to mind), but the emphasis on presence, connection and community has got to be central to an understanding of social networking sites. But something's missing and that something is to do with acting upon each other, sharing and building understandings, playfulness and the creative juxtaposition of ideas.