Membership can be tightly controlled through scoping Social Objects. When a scoping Social Object is created, a list of approved members is defined. When someone then creates a Conversation from that Social Object, only people defined in the membership list can be added—no one else. This ensures that sensitive or private information is not inadvertently shared with others who might not have a need to know.
Not all deployments of Oracle Social Network have scoping Social Objects. Your application administrator can tell you if yours does.