iOS has a prompt before your address book/contacts are shared with any app and apps will always work without it (required by dev guidelines). However note that

iOS has a prompt before your address book/contacts are shared with any app and apps will always work without it (required by dev guidelines). However note that this article is not referring to the Facebook mobile app accessing the mobile contacts -- this is about their service logging into a person's email service (like GMail) and downloading their email contacts.