... the user is not just signing in using her Google Account, but is also sharing specific information from her Google Account with the Relying Party website. This information may be either static fields (using Attribute Extension) such as the user's email, first and last name, preferred language and country, or allowing access to any available Google Data API such as the user's Contacts List, Web Albums, or Calendar (using OAuth)...I am concerned about authentication bugs causing me to be locked out of my Google account, so I'm proceeding with some care.
Sunday, June 07, 2009
Google's summary of their OpenID and federated authentication approach
This is what enables me to auto-authenticate with Facebook when I'm logged into Gmail. I've linked the accounts from Facebook using this Google API: