Abstract: Much of what we understand about the notion of online learning communities and how they develop, grow, and die away is based on examinations of formal online learning environments— primarily post-secondary courses managed by institutions of higher learning. As effective as formal environments may be, paying exclusive attention to them limits our understanding of the nature of social learning. Informal learning environments, by contrast, can tell us a great deal about how people learn together in natural settings, and can teach us a great deal about what happens when the authority for learning is entrusted to learners. This presentation considers what we have learned about learning communities in formal and informal online environments and speculates about what is at the heart of how learners make use of social interaction for the purpose of learning.