Starting with the upcoming iOS 6, Apple will requires apps to get explicit user permission before accessing contacts, calendars, reminders and photos.
According to a MacRumors report, the following was added to the "Data Privacy" section in Apple's iOS 6 Release Notes:
In addition to location data, the system now asks the user’s permission before allowing third-party apps to access certain user data, including:
- Contacts - Calendars - Reminders - Photo Library
For contact, calendar, and reminder data, your app needs to be prepared to be denied access to these items and to adjust its behavior accordingly. If the user has not yet been prompted to allow access, the returned structure is valid but contains no records. If the user has denied access, the app receives a NULL value or no data. If the user grants permission to the app, the system subsequently notifies the app that it needs to reload or revert the data.
* Image via MacRumors.com.