Open vs Private groups on EdNA Groups

EdNA Groups (based on Moodle) has proved to be very successful in the short 6 months it has been providing a free service to the Australian education and training community. EdNA Groups is updating its services with some custom enhancements which will ultimately enhance Moodle upgrades.
One excellent example is the Online Mentoring Network providing resources, activities and discussion about "exploring tools for, and methods of, mentoring and coaching online." These include collaborative resource wikis on topics such as emerging tools and technologies and mentoring resources.
So what's the controversy?
Leigh Blackall (Teach and Learn Online blog) has posted thoughts on whether EdNA Groups should provide open or private spaces with an interesting reference to longevity of the resource and the usefulness of social software available elsewhere. Value of folksonomy and aggregation possibilities!
Leigh believes that "... teachers and educationalists would be better spent engaged with the open Network, learning the popular tools and understanding the nature of the Internet..." It is sheltering individuals and groups from 'global conversation'.
I use EdNA Groups, my (work) Moodle site and various social software tools and can see EdNA Groups filling a valuable need in providing opportunities for collaborative workspaces, both open and closed. Some developing communities value the ability to conduct discussions and share resources in a private space, protected from the glare of cyberspace.
I also use and promote social software and Web 2.0 tools in facilitating global dialogue and professional learning.