I've been reading about new security issues in the field of social networking recently. It's a very interesting topic ranging from identity related threats to social threats such as stalking, bullying or corporate espionage.
New social networking software will introduce a security break in traditional security practices and operations. It adds a new aspect too, those organizations responsible for security will have to change and adapt their security plans to reduce impact (business mapping, information leaking ...) and implement effective countermeasures.
Perhaps it's time to develop new security tools. Can you imagine a "social firewall"? Good paper in this topic is ENISA's position paper balancing technical and social recommendations and countermeasures. You can read it here.