What actually happens when you let apps track your activity?

With all this talk of targeted advertising, some argue that privacy advocates are tilting at windmills. After all, they ask, what's so bad about more relevant ads? If I have to see ads online regardless, isn't it better for them to show me things I might actually want? While that's an understandable line of thought, the dangers are more to do with what happens when your data is combined from multiple sources and used in combination with data from billions of other people. These knock-on effects extend beyond any individual.

Targeted ads aren't about helpfully homing in on your general needs and desires. They're just as often about manipulating your emotions or behaviors. If the data collected from you shows that you're more likely to make a big purchase when you're sad or angry, then getting you into that agitated state becomes a desirable goal.

In aggregate, data collected from billions of devices can enable society-wide changes. By now, the average person is likely familiar with some of the ways big data has been used to influence politics in the US and around the world, with the most notable such example being the Cambridge Analytica scandal in which the eponymous data firm used data collected from millions of users to sway the 2016 US presidential election. That data was collected by convincing users to give a survey platform access to their own profiles and those of their friends.

Beyond all of that, there's just no upside to having your name, home address, email and other identifying information available for purchase. It's not only advertisers who want that information. From stalkers to hackers to law enforcement, you can't control who the buyer will be. 

As mentioned, law enforcement has used location data from brokers to prosecute people for exercising their reproductive rights. Under the direction of Kash Patel, the FBI has been purchasing user data en masse from commercial brokers. Speaking of abortion, activists were found in 2024 to have purchased data on users who visited Planned Parenthood locations in order to target them with abortion misinformation. These are but a couple of the countless ways your data can be used against you.

Ultimately, the best advice is to resist giving your data to apps. Even if you can't prevent apps from tracking you entirely, you can make it much more difficult. Routine privacy checkups are also a good idea  — go through your app permissions once in a while and see which can be revoked. If you must give an app permissions in order for it to function, ask yourself whether your life would be significantly harder without that app. And, in general, you should delete any app you do not use, as you never know which of them may be silently collecting data.