John Gruber on the debate on how to best implement a method for users to explicitly allow iOS apps permission to access the Contacts:

Every dialog box has a cost.

The same is true of any click, tap, swipe, notification, chime, prompt, or menu. The more of them, the higher the cost and the harder it is to give your users the best experience. Finding the optimal system is not easy – hence the debate. But what is clear from the Path controversy is that not having a method to control access to private data is the highest cost to ones reputation.