They know if you've been bad or good...
"Over the weekend, Dave Winer wrote an article at Scripting.com explaining how Facebook keeps track of where you are on the web after logging in, without your consent. Nik Cubrilovic dug a little deeper, and discovered that Facebook can still track where you are, even if you log out. Facebook, for its part, has denied the claims. Regardless of who you believe, here's how to protect yourself, and keep your browsing habits to yourself. "