The entire point of Yellowdig is to build learning communities where people can help one another. Yellowdig uses a format that is familiar to learners and that they enjoy using in other parts of their lives. With some small rewards for participation, and by making the experience a fun and different way to engage with the content, learners will find interesting ways to support each others' learning with limited instructor effort.
Why? The pedagogical principles that govern classroom discussions also govern Yellowdig discussions. Your job as an instructor is not to drive or constrain dialogue, but to broaden and facilitate it. As former university instructors, we understand the temptation to micromanage conversations and control topics of discussion. But successful Yellowdig conversations are just that: conversations. It's not about grading or assessing; it's about inspiring students and spurring original thoughts. In a word: Be a bit less didactic and a bit more Socratic.