Farhad Manjoo, reporting in Slate:
Mark Zuckerberg would never acknowledge this, but I think it will ultimately benefit both his site and its users if we adjusted our expectations about "privacy" there. You should approach Facebook as cautiously as you would approach your open bedroom window. However restrictive your privacy controls, you should imagine that everything that you post on Facebook will be available for public consumption forever. If you follow this simple rule, you'll never be blindsided.