As of today Google offers a API to sync with your Google contacts. In the quest for the Holy Dataportability Grail, the syncing of contacts through out different ‘contact’ services is the next big thing. Everybody owns several buddy- or contact lists. Keeping them in sync is hell, even when your using Plaxo or a Plaxo-like service.
Google’s API lets you read all of your contacts and use them in another application. The changes made in that application can be written back in you Google contact list. The API is part of Google’s Data API project and uses AtomPub as a format.
With opening up their contact information Google is the first of Internet biggest to create a portable contact list. For social networks, their user base are their capital so the question is whether social networks wil create contact list portability? Probably, opening up will be inevitable since portability is the future. When you can take of your contact list from one service to another, the only reason for using a social network will be what kind of functionality they offer. At the moment you pick a network because of the fact that all of your friends are on it. They next battle will begin when contact portability is widely excepted.
Of course Google’s Contact API is no portability standard yet, is doesn’t help you switch from GMail to Yahoo Mail. But it’s a start.Lots of people are working on syncing services for your contacts, a standard will only arise in the near future. More on contact list portability at the DiSo Project.