This study aims to identify the formulation differences of groups in two online activities in a university course with different strategies by using social network analysis. Specifically, the connections within the members and identification of brokers were analyzed. Whilst the group enhancing a "community of practice" in WeChat by assigned posting showed larger evolution on the social graph, it lacked active involvement of students' friends and structural holes and their diameter were shown to increase towards the end. Another group enhancing a "personal knowledge network" in Twitter by their free posting showed no ties with any social actors, implying a cold-start and problems of sparsity in the social communication. From the discussion about brokers, we concluded similar future needs to develop their social skills to promote itinerant and liaison brokers to evolve learning groups socially.