This article about the lack of true solutions for how business users actually use their mobile address books and manage contacts has attracted a lot of attention. I think he gets it right in his "key features" list.
I love this quote from the article: "Facebook is working on something in this area, but won't say what. Yesterday at the GigaOM Mobilize conference in San Francisco, an audience member pointed out to a panel that a phone's address book in fact is that person's social network. Facebook VP Chamath Palihapitiya responded with: "That's a great observation. Stay tuned." That sounds to me like Facebook will be announcing something in this area soon."