I have come across many, many questions regarding syncing contacts with Ubuntu One. Unfortunately this is not possible in 12.04. I even asked ubuntuone-support and recieved this:
HI, We are completely redoing contact sync. Contact sync, I'm afraid, will not be available in Ubuntu 12.04. We are optimistically hoping for contact sync to be back in 12.10. The new service plans to be a great improvement. We do sincerely apologize about any inconvenience. Thanks, ([email protected])
However, I was wondering if anyone knew if older distro versions were still able to sync - as it might be a good work around to install Ubuntu One on a 10.04 Live CD and then export the contacts as a .vcf after sync.
I'm sorry, and I may be mistaken, but I don't believe that this feature is present on the Ubuntu One servers anymore, so just running an older release won't be helpful. They decided that the old approach wasn't workable.
In order to again provide the feature, both server and Ubuntu clients will have to implement the new approach. I think that's why they refer to 12.10. The servers will need to implement a database in the cloud, and the clients will need to communicate with it.