Really good idea. One of the things that I found lacking (in retrospect, now that you mention it) in Coursera when I used it was that study groups weren't an official feature. I'm sure people made them unofficially in the forum, but it wasn't an official part of Coursera. I think it would really elevate MOOCs to another level if you could have face-to-face Skype-like study groups with other students during assignments.