Encouraging students to be more social with each other via course wall exchanges
One idea that I have employed with adult learners, is to gently redirect them when the opportunity arises. For example, if a student asks me a question that I know is relevant to other students, and also doesn't require my decision making skills, then I will ask them to post that on the wall, and to address it to their colleagues. Then, to keep things moving, I might also encourage one of their peers to respond.I might pick another classmate that I know (or I might guess) has a certain POV on the question posted. To everyone else, this "crafted discussion" is inspiration, and shows a certain level of activity. Yes, it is contrived, but it can motivate others to enter into authentic discussion.

Also, a rating system that encourages good answerers to build reputation might help. ;-)