Where the article enumerates the reasons one might not want to share one's entire address book, it leaves out the one most important to me. If I allow an app access to my entire address book, it can see atrributes on an entry that I feel I should not leak such as birthdate and home physical address. Address books need a finer grained way to express such access control. Even when sharing a contact with a third person and not a service, I might not want to share the entire address book entry for a person.