By Hossein Rahnama, contributed to The Globe And Mail

Any iPhone user who updated their operating system recently discovered a new and truly remarkable privacy feature: the option to shut down any app’s ability to track you across your other apps. It’s a full-screen popup that essentially asks you whether you want to let Facebook or Twitter or any other app continue to gather data about you from your iPhone. 

The feature has provoked a minor existential crisis among many tech firms, including Facebook, that make their money by gathering information about you. How will they know which sports gear ads to put in your feed if they can’t check your fitness apps to see if you are running, cycling, or playing tennis these days? 

The stakes are far higher than a few pairs of running shoes. The market for our personal data has risen out of thin air in the past 20 years to become a trillion-dollar global economy, and this kind of surreptitious data tracking is routine in the industry. One analyst estimates that, if 80 percent of iPhone users say no to tracking, it could cost Facebook as much as $2 billion in quarterly revenues. 

But if Apple is effectively shutting down some data revenue streams, it is also opening up new ones—and not merely for Apple itself. Once people have more control over their personal data, it will begin to shape a world in which they get something in return for sharing it, rather than always giving it away for free.