Facebook is notified whenever you visit one of the more than one million sites on the web that use Facebook Connect and has a history of leaking personally-identifiable information to third parties.
Turn off the flow of your data to them!
Facebook Disconnect blocks all traffic from third-party sites to Facebook servers but still lets you access Facebook itself.
Instructions: The add-on displays an icon in the location bar if a page initiates Facebook requests. You can block or unblock the requests by clicking the icon. Your preference will be remembered the next time you’re on the site.