> (Zuckerberg reluctantly acknowledged that Facebook gathers information on people who aren't signed up for Facebook for what he said were "security purposes.")

> (Zuckerberg reluctantly acknowledged that Facebook gathers information on people who aren't signed up for Facebook for what he said were "security purposes.") This sort of information gathering is necessary for DDoS/Spam/Fraud prevention and so on. I'm not saying I trust Zuckerberg wasn't hiding something else, but also I understand why he didn't want to publicly comment on the heuristics they use to combat attackers. Although at this point I don't know why Zuckerberg would be obfuscating if they really have detailed advertising profiles on logged-out users. (What would said advertising profiles be used for? Selling them to other advertisers?)