Facebook specifically and individually tracks all people, even those who aren’t FB users. Using the opt-out mechanism you’re even worse off, since setting the opt-out cookie makes you uniquely identifiable (again).
During the opt-out process, Facebook sets a long-term identifying cookie and then uses this to track visits to pages that have a Facebook social widget. In other words: “for those individuals who are not being tracked by Facebook (e.g. non-users who have never visited a page on the facebook.com domain, or Facebook users who clear their cookies after logging out from Facebook), using the ‘opt out’ mechanism proposed for the EU actually enables tracking by Facebook” (emphasis in original).
When you opt-out …
[…] Facebook promises to stop collecting browsing information, or use it only specifically for the purpose of showing advertisements.”
So, of what use is it then?!?