In questioning on Capitol Hill today Mark Zuckerberg said: "In general we collect data on people who are not signed up for Facebook for security purposes." Can someone explain what this means? If you don’t have a Facebook account why would Facebook be collecting data on you for security purposes? What security is he referring to? At first I thought maybe he was referring to using Facebook to log into other apps/services but in order to do that you have to have a Facebook account (even if you never post stuff to it). Also, how does Facebook get data from someone who doesn’t have an account. If you see Facebook content on another website do you even have the ability to ‘like’ something without having an account and being signed in? I’m confused as to how Facebook can get information on non-users outside of buying it from a 3rd party source (which Zuck claims they no longer do).