“Apps that collect or transmit a user’s contact data without their prior permission are in violation of our guidelines,” Apple spokesman Tom Neumayr told AllThingsD. “We’re working to make this even better for our customers, and as we have done with location services, any app wishing to access contact data will require explicit user approval in a future software release.”
A fair and reasonable response from Apple.
In terms of usability and actual user comprehension, I believe the alert box is the best way to ask users that a certain permission (such as permissions for Location and Twitter account details) is required. The main difference with iOS and Android is that iOS asks you for permission when you are performing a task which requires the permission at that time. If you never use a particular feature of an app which requires the Address Book permissions, you won't be asked for that permission. Android asks you for permission(s) upon app installation which are usually blindly clicked through by users who just want to start using the app they downloaded.