Q:

How can I use SSO to login to my Ubuntu machine instead of Local User Management

Instead of maintaining local user accounts, I would like to be able to use Ubuntu SSO (Ubuntu One) accounts to authenticate the logins to my Ubuntu machine.
Any chance?

A:

The topic was mooted at the Ubuntu Developer Summit in late 2011. OMG! Ubuntu! covered the topic. 
The Ubuntu One team liked the idea, but there are many technical challenges before logging in with SSO credentials will be possible. Don't expect to see it anytime soon.

