Facebook, since its mistakes with the Beacon advertising incident, has rolled out one of the most robust security systems for any social network, which allows users to control who sees what information about them with great specificity. Take a look at Facebook's privacy features and how to set yours.
News Feed and Wall Settings
Your Facebook "News Feed," keeps you up-to-date about your Friends' actions (Twitter updates, photos, new friends made and more) on the social network. Facebook privacy settings let you regulate what your Friends can see. At the main privacy settings page, click on "Newsfeed and Wall." Click on the tab "Actions within Facebook" and check boxes to designate which of your actions Facebook friends can see. Tip: Don't uncheck everything; it dilutes the value of Facebook.