Spot the difference...
Crossing the Chasm is a widely-read marketing book by Geoffrey A. Moore that focuses on the specifics of marketing high tech products.
One of the ways to ensure that a product does cross the chasm from early adoption to stardom success is to deploy "whole product design". In essence, this means designing something that really does meet the user's expectations/requirements entirely, at least for features that matter.
Spot the difference
The above slide from one of my training courses/seminars shows an "old-fashioned" journal address book on the left, and a mobile phone address book on the right. Can you spot the difference? Most seminar attendees can't see it.
What's missing from the left is a pen, or something to enter the addresses with! There are lots of people with address books and pens who can make entries, but who can't store entries in their phones. In my opinion, most mobile address books are not whole product designs. A simple option to get operator assistance to enter addresses remotely might be one solution. There are others. Think about it for yourself.