Although there is strong evidence that massively multiplayer online games (MMOGs) constitute environments of social interactions and effective learning, we currently lack the tools for investigating the effectiveness of the social networks emerging as well as the cognitive aspects and knowledge acquisition such environments involve. Within this context, we present a conceptual framework for the investigation of the collaborative problem-solving processes emerging in such environments and we apply it in the investigation of a number of MMOGs through interviews and virtual ethnography. Our findings suggest the balanced convergence of multiple factors, such as the mechanics of the game, the design of the tasks, the collaboration and competition affordances and the content of the game, for the constitution of an effective environment for collaborative learning. (Contains 2 tables and 9 notes.)