Since their emergence in 2005, Web 2.0 technologies have been advanced as potentially transformative in the area of education in general and foreign language learning in particular. Web 2.0 technologies are presenting new opportunities for developing diverse online learning environments and enhancing interactivity, participation and feedback between students, their peer groups and teachers. This article examines one of the most significant Web 2.0 tools, Social Networking Sites (SNS), and focuses on Livemocha, an example of an online community specifically aimed at encouraging collaboration between foreign language learners. Results from the ethnographic approach adopted in the paper indicate that: (a) SNSs can be used by language learners to explore new relationships rather than merely maintain existing ones and that (b) longitudinal studies are required to achieve a better understanding of the complex processes of mediation involved in online community formation and maintenance.