"public" "private" "open groups" "closed groups"
I think the distinction between "public" and "private" may not be clear, e.g. how does this concept of oppositions link to "open groups" vs. "closed groups"? Does a "public" approach imply that the people who work on something show this to anyone else immediately AND anyone can join in as they please? Or is there no interrelation between those two sets of concepts in our context? If there is not, why not? ;-)
I am of the opinion that closed groups are required for creating quality content. While creating any content the author must have certain ideas and he/she may need some time for implementing his ideas interacting with some limited individuals who are part of the group. The content may be kept open only after this completion. Once it is open then anyone can edit. We may keep some time frame for such closed activity.