I found facebook much better to bond with the girls. We are all really close. I don't understand the whole 'privacy' argument as these groups are closed and no one at all can see that you are a) a part of one and b) what you are saying.
I also stopped posting in my due date group when there were comments from the ones who didn't want to go on facebook about how much 'better' it was now and how they could keep up. That offended me and I felt like we weren't even welcome there anymore because we like to talk.
As for the private social groups on here, I just feel not 'cool' enough when there is talk about something that happened on one and I'm not part of it.