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, (firstname.lastname@example.org)
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.