I've never been a member of Facebook and don't have any Like Buttons on any of my sites. But they still get quite a bit of traffic that appears to come from Facebook, according to my logs. But when I try to track a visit back to a specific page on Facebook, I always get a message that says I'm forbidden to see the page.
Does anyone know of a way for me to determine the specific source or sources of this traffic that appears to come from Facebook?