I think it’s a very good move by Apple. With them advertising that their products are secure and private, allowing users to choose whether to let an app track your activity is a good feature. Many apps (ahem **facebook**) tracked your activity to “give personalized info” but they mostly used the data to show you ads. After this feature was enabled, most (96%) of users turned off tracking. I believe if Apple starts doing things like this, privacy features would grow a lot.