Online data tracking is so pervasive that the concept of internet privacy seems almost oxymoronic. Who is watching us, and what do they want with our data? A t a glance, Facebook appears to be free. Its registration page, after all, doesn’t ask for your bank details, nor does it even ask for a donation. Yet Facebook doesn’t give away access to its platform for nothing. Your name, your gender, your date of birth, your hometown, your email address; these are your payments to Facebook.