Social networks provide rich opportunities to interact with friends and other members. While research on motivations and interaction design help explain what makes online communities successful, the influence of trust on social location technologies and interactions that integrate online and off-line activities remains unclear. Drawing from research on information systems, social psychology, and social networks, we identify the drivers of users' trust in social location artifacts and other subscribers. We will test our hypotheses on Facebook's Places application by connecting surveys to actual usage data. We expect trust in the artifact to depend on usability, situation normality, perceived critical mass, and referrals from trusted sources. We also hypothesize that trust beliefs toward other users-split into friends and everyone else-will depend on instinctive feelings of trust, rationalizations that others won't do harm, and structural assurances. Implications for theory and practice as well as limitations and future work are discussed.