While we use the term "social network site" to describe this phenomenon, the term "social networking sites" also appears in public discourse, and the two terms are often used interchangeably. We chose not to employ the term "networking" for two reasons: emphasis and scope. "Networking" emphasizes relationship initiation, often between strangers. While networking is possible on these sites, it is not the primary practice on many of them, nor is it what differentiates them from other forms of computer-mediated communication (CMC).
This seems to be very consistent with the distinction that Facebook is making when they say the site is a "social utility that connects you with the people around you." The research my colleagues at MSU and I have done addressing Facebook usage suggests that, at least among the population of undergraduates we study, Facebook is most commonly used to either a. articulate existing relationships or b. develop nascent relationships that are built on some shared offline connection. Although it does happen, we find that it is far less common for these users to friend complete strangers. Additionally, as we argue in a new paper, using Facebook to find out information about weak ties may be beneficial to users in ways that connecting with existing close friends or trying to friend total strangers may not be.