Facebook allows you to add extra third party applications to your profile. These have a wide array of uses including giving you a weather forecast, allowing you to doodle graffiti on another person's wall, or telling people who your top friends are.
Users should exercise care over which applications they add to their profile as information can be shared with the application's author. Facebook has published terms of service to inform developers of what is and is not acceptable behavior, but there is always the danger that people will abuse the ability.
There are 7 ways to display applications that have access to your profile in the main drop-down menu—it is worth going through these options and clicking "edit settings" for each application to see their permissions.
|Events, Gifts, Groups, Links, Notes, Photos, Video—and all other applications
||Privacy: "Only Friends"
||As a minimum, we recommend that the information posted by these applications is only shared with friends. Always consider that material you post on the internet may end up in someone else's hands - if the material is likely to compromise your security or embarrass you later think twice about posting it online!