Social network sites such as Facebook and MySpace have become increasingly important Internet destinations. Their reliance on the concept of "friend" has raised questions about what that term really means in this context. This talk offers an overview of the emerging research on the interpersonal dynamics of social networking sites and focuses in particular on a survey study of friendship in Last.fm, an international site focused on music listening. This work seeks to identify how developed these relationships are, how Last.fm fits into the communication patterns of these partners, the role of musical taste in predicting closeness, and the range of motivations and connections reflected by these relationships.