Social Groups
 

Sorry if this is a dumb question. Is there a way to make it so that only the people in the group can read what's posted in the group?

I would say Invite Only adds this functionality but I don't know of any other way to do this off the top of my head.

I asked the same question at vbulletin.com and the invite only does not stop anybody out of that social group from reading the comments. It just makes it a invite only by the member that started the group. I wanted the same thing, but for now, I guess its a no.

Try going to ACP-->Social Group Options and setting Allow Join-to-View Groups. If you have already set up groups you wish to make private, Edit Group will now show an option for Users must join to view the content.

There is only one problem with that. In the above option it has this:

Enable Social Group Messages

If you select this options, members of each group will be able to post messages in the group. Users who are not part of the group will still be able to read the messages.