When implementing these features, I felt like iOS had given me far
too much access to Address Book without forcing a user prompt. It
felt a bit dirty. Even though I was only accessing the data when a
customer explicitly asked me to, I wanted to look at only what I
needed to and get out of there as quickly as possible. I never
even considered storing the data server-side or looking at more
than I needed to.
This, apparently, is not a common implementation courtesy.