"What's on your mind?" It's the friendly Facebook question which lets you share what you're thinking and what you've been up to. It's also the question that unlocks the details of your life and helps turn your thoughts into Facebook's profits. Four Corners explores the world of Facebook and how your data is being mined to drive the huge success of the social media giant. Reporter Peter Greste examines the Facebook business model and shows why your private life is making them billions. The program investigates how Facebook has the ability to track much of your browsing history, even when you're not logged on, and even if you aren't a member of the social network at all.