I want to create a Ning group for colleagues. Excuse my ignorance but I have these questions...
Can there be groups where members require approval before joining?
Can all forums and posts be visible only to members?
Can you enter invitations in bulk i.e. five e-mail addresses separated by commas?
OK, I know the answers to 1 & 2: Yes. I'll check on 3. Just by coincidence tonight I started http://education.ning.com, a social network just for helping educators start Ning networks. You might consider joining there as well (you'd be member number three!).
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OK, I don't see a way to comma-add invitations, but as you can see from http://www.classroom20.com/invite the invitation form is really fast and easy. Gina from Ning said in late July: "We're going to provide more and more ways to bulk invite and/or import members from another services in the coming months. It will get much, much easier :-)"