Worried about Facebook or other sites tracking your web history? Then all you need to do is open a new private tab in Opera (or a new private window in Firefox) and simply load Facebook into that, and then pin it (Opera lets you pin tabs) – then just make sure you use that tab for all your facebook browsing. Simple but effective :p
Update: Looks like facebook REALLY don’t want you to do this, because now, when you log in to facebook from a ‘private’ tab or session you have to jump through hoops to identify yourself!! Try it and see!