ShorttitleAs social network sites like MySpace and Facebook emerged, American teenagers began adopting them as spaces to mark identity and socialize with peers. Teens leveraged these sites for a wide array of everyday social practices—gossiping, flirting, joking around, sharing information, and simply hanging out. While social network sites were predominantly used by teens as a peer-based social outlet, the unchartered nature of these sites generated fear among adults. This dissertation documents my 2.5-year ethnographic study of American teens'' engagement with social network sites and the ways in which their participation supported and complicated three practices—self-presentation, peer sociality, and negotiating adult society. My analysis centers on how social network sites can be understood as networked publics which are simultaneously (1) the space constructed through networked 2 technologies and (2) the imagined community that emerges as a result of the intersection of people, technology, and practice. Networked publics support many of the same practices as unmediated publics, but their structural differences often inflect practices in unique ways.