One of the issues that drove my choice of a PhD topic, and steered the way I thought about how social interactions work, was the way existing online learning systems tend to create social spaces. It's starting to change, but for a long time online learning systems kept the social aspects separate from the rest of students' learning. Even the innovative tools that linked social interaction with interactive learning tools and materials were still small systems, separate from the vast bulk of a student's online learning. Normally, students would be given a discussion forum attached to each unit of study, and it was hoped that they would use them constructively. There was minimal integration between these spaces and the other online spaces students engaged in. You end up with a space that looks like this:
And what's worse, each unit of study is a separate little mirror of this - so not only are the social spaces separate from the course material and other activities, they are also separate from each other - a conversation in one Unit of Study cannot be linked to a conversation in another unit; and when the semester ends, the units end, and the conversations are archived or deleted. It's little wonder motivation has to be drummed up by teachers, and the common solution is to make the forums compulsory.
My approach will be a bit different. Rather than creating stand-alone social tools, the goal is to embed them throughout the curriculum, so that wherever students are, there are social tools available for collaboration and interaction with peers. The above diagram becomes a little more like this:
-- each page has a little bit of interactivity attached; students socialize where the content is, not in specially constructed separate spaces. Furthermore, those slices of interaction can be linked up in other places as well - a student's profile page will contain an activity stream of their interactions across the curriculum; and student group pages can also contain activity streams of members.
The thought behind this is that by reducing the barriers to participation - if collaboration is only a matter of clicking or typing on a page the student is already visiting, there is hardly any effort at all to join in - students will be more likely to collaborate of their own accord.

