Marco Arment has chimed in, from a developers perspective, on the subject of Path's using Address Book data without asking the user permission first:

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.