I believe this feature already exists here. its called social grouping. you start a social group. set the social group up as invitation only and then only you and those you invite will be able to post in your group. others will be able to see but only those you invite and join will be able to post.

there is also chats, it used to be where members could make their own private chat rooms but that was changed, you have to now apply to be a chat host if approved then you get to host chats in the chat rooms

this link will lead you to other links about the chat rooms.

http://forums.psychcentral.com/chat-...ted-rooms.html

there is also a forum for chat announcements where you can find more information about the chat rooms.