(This may be a response to multiple discussion threads so please forgive that, it all ties together in my head.)
In reading the responses here, I wanted to raise the issue of audience again. I am professionally interested in ed tech. Unlike many of the MOOCs out there which I might start out of curiosity or interest, ed tech is something that I would actually apply and something quite practical. For example, just in creating a MOOC we will be engaging in quite a few forms of ed tech. I am wondering if the target audience is primarily like me. Is the target people who use ed tech or who want to learn, people for whom this would be a form of professional development? (From what I've read, I really get the feeling that most of the MOOCs out there are a little less hands-on or immediately applicable, more for interest-level participation.)
If the target audience is people who use ed tech and who could be putting what they learn into practice (probably Fall semester or Spring/Summer if it rolls in Winter 2013), then we may have more investment from at least some participants. Also, those who are participating in the discussions prior to the course are more likely to have more investment so there may be a pre-existing pool of people willing to help drive things forward as mentors, group leaders, etc.
If we are looking at people who are in a field that would actually use ed tech as primary audience, then I definitely agree that more practical application and creating as opposed to solely discussing would be useful. For example, Learnist boards linking articles about using social bookmarking, with commentary about that issue.
It makes me wonder about groups focused around forms of ed tech which produce a product which can share their knowledge with people who didn't participate in that group. That way the pedagogical discussions can be quite focused, people can participate in multiple groups if they have time/energy, but they can still get the benefit of those groups if they can't participate.
(I like the idea of groups based around people's fields but it could become unwieldy or be an organizational frustration if we have uneven numbers or awkward groupings.)