I think it would be fantastically useful if upon first start up of Ubuntu a wizard could come up (with a simple 'cancel' and 'Do not show this again' option for those not interested and is then placed under preferences) where you can tell it as much (or little) information as you wish such as your email address, location, IM accounts as well as give you the opportunity to connect with Facebook, Twitter, Last.fm, Flickr etc.
Then Ubuntu could take this information to automatically sync your desktop with these services, in ways such as:
Bringing your contacts together in the address book
Adding the IM accounts to Empathy
Adding Social networks to Gwibber
Allow viewing albums from social networks in a photo manager
Enable scrobbling on Last.fm
Set the weather corresponding to the location.
It could even be done through Ubuntu One so that simply logging in to Ubuntu One on another computer could offer the option to import the settings.
I believe this is a great method because it will allow new users to Ubuntu to set up all of their networks and really give them an initial wow when they start to use Ubuntu and everything is already there for them, but will not intrude on people who are not interested in this kind of service, they can just cancel the wizard and move on with no repercussions.
