The following article is a couple of years old, but still spot on regarding what we can and cannot do "publicly" on social networks and then, still, believe that we maintain our privacy protection. Obviously, there will continue to be court cases and new case law created for the Information Age that includes a clearer understanding of what consitutes "privacy" and then the publication of that information that removes our protection.
This is all especially important during this era where so much of the Internet is "free" and the collection of our data - posts, pictures, profiles, is handed over by us to the social media provider.
The beat goes on!
The Law of Privacy on Social Networks