Does Google want to create a Google Passport, like Microsoft did (now Microsoft Passport is called Windows Live ID)? If you login to your Google Account and go to My Account, you'll see a strange link that says Change authorized websites and points to a page that gives an error: "Currently there are no third party sites authorized to access your account."
So that means in the future third party sites will be able to access my account? There are many Firefox extensions that ask my Google username and password to check my mail or my bookmarks. Using this simple sign-on, you'll be able to authenticate once and have access to other sites that use the same authentication service. It's easy to have less accounts, but these third-party sites will have access to your personal data.
Microsoft Passport has failed to gain too much market share, the only major sites that use this authentication sytem are Expedia and Hoyts. Microsoft Passport was supposed to be used as a central repository for personal information, including credit card details.