I've got a friend who works as a correctional officer in a German "open prison". When the inmates leave for home on weekends some of them are forbidden from consuming alcohol, drugs, contact certain people, visit certain areas.

According to my friend the most effective tool to check up on those inmates is Facebook. Quite a few of them just can't resist to post drunk party pictures, brag about stuff they shouldn't be doing, etc.

Another way they use Facebook is to detect if someone's using a mobile phone - which are forbidden on the compound: Simply check the inmates' profiles and see which inmates who are not on leave are online.

There's that quote that says that Facebook made possible what KGB, Stasi and the likes couldn't ever dream to achieve. So yeah ...