There was much talk at Global Messaging about network address books. These are address books hosted by your mobile network provider on your behalf, instead of on your phone or SIM card. Check the Openwave Network Address Book for one of the offerings being touted to operators.
The rationale is that this allows the network to augment the contacts in your address book with an advanced set of features. Presence will be the most obvious feature but also close integration with other services will enrich other messaging and calling services.
It's a great idea from a feature point of view, but are users really going to go for it?
Privacy is the one consideration. Are people going to resist storing the details of who they know and communicate with on their operator's network. Given the success of Hotmail, Yahoo, etc I can't see this being a huge barrier. The convenience of having this access list wherever you're logged seems to have won over the majority.
The vision of the one address book for all time is probably going to be more challenging.
There will probably be a perception of being locked in to the mobile network. What happens when I move? Can I port my address book in the same way I can port my number?
Further, as a business user, my contacts are all in our in-house Exchange server. I can't imagine authorising uploading our internal contact database up to Vodafone's network, however convenient it would be.
So we're stuck with multiple address books, unless we can find an alternative that satisfies both privacy concerns and network functionality.
One route would be for the networks to adopt an open standards approach. Allow your network address book to incorporate both their database as well as other address books using open protocol standards like LDAP.
A request to your network address book would make an subsequent request to our corporate address book and add the network value, like presence, location on the way through.
While this would still expose our corporate address book to outside world it would be in a controlled manner to a trusted party (the network operator) and allow us to switch off or change networks as required.