Why isn't my phone supported by the contacts sync service?
If you have an Android phone, then you can search for the Ubuntu One contacts app in the Android marketplace. If the app is available there then your phone is supported.
We depend on our mobile contacts sync technology provider, Funambol, for most of our mobile clients. They put out new updates fairly regularly and this normally includes support for more mobile devices. We'll be sure to update our blog with details on the next release we put into production, including support for additional mobile devices: http://voices.canonical.com/ubuntuone