N.Y. Times: Tim Cook threatened to remove the Uber app from the App Store
Eventually, Apple discovered the ruse. And while Cook was calm during his meeting with Kalanick, the Apple executive was firm with his demand that Uber immediately stop violating Apple's regulations. Cook made it clear in no uncertain terms that if Uber did not stop tagging iPhone users, he would have the Uber app removed from the App Store. Facing the possibility of losing access to millions of iPhone users around the world, Kalanick agreed to stop the tracking of Apple iPhone handsets.
Uber says that the reason it tagged iPhone users was to prevent fraud. In China, stolen iPhone units would have their memories erased and would end up being re-sold. Some crooked Uber drivers would then create phony accounts based on the stolen handsets, and request rides from those fake accounts. Using a process called "fingerprinting," Uber could identify an iPhone even when its memory was wiped. And since this move violated Apple's rules, Uber made sure that those inside Cupertino couldn't discover what Uber had done.
However, Apple employees outside its headquarters did find the "fingerprinting" code which led to the showdown between Tim Cook and Travis Kalanick. At the end of the day, both sides won. Apple got Uber to remove the tagging, and Uber got to keep its app in the App Store.