I see this as a bit of overkill. Don't get me wrong, I would gladly like to learn more astronomy, but I don't think the best way to do it is through this forum (as an organized course; I do it through discussion). I consider forums as places of discussion and debate (like the Roman Forums), not a place for a formal class. A thread like this is a great thing, since we have people like Michael Richmond guiding us to the best online places of astronomical interest. I really am thankful for that, but I do not think that it's feasible to organize a class on an online forum.
PS: An aside: you would have to deal with people registering continuously, and they might want to join the class, even though the class is in the middle of the course. Perhaps this has been dwelled on already, I don't know.