This paper reports on a PhD study about informal second language learning in online communities (Livemocha and Busuu). In these communities learners autonomously seek opportunities for telecollaboration with Native Speakers (NSs) in the absence of teachers and pedagogical tasks, and in an informal context. This paper focuses on learning and social resources of these communities as a support for tandem activities. The methodology adopted had an interpretative framework and consisted of six phases. Results showed that these online environments have a potential for learners to engage in naturalistic repair trajectories. The conclusions that can be drawn from this study are that, despite today's flourishing of social media and new technologies, tandem language learning still presents the same challenges and more investigation is required on the adequate support learners need. [For the complete volume, see ED571330.]