Google's OpenID system breaks some assumptions in CiviCRM standalone

Google's OpenID implementation uses a common URL for everyone, so it breaks our assumption that the OpenID URL is unique to the user. There may be a behind-the-scenes unique URL, but no one will know it nor is it easily obtainable. This is primarily a problem when people are adding new users to their standalone instances and want to add someone's Google OpenID.

I don't know what the solution is yet, but we should figure this out and get it resolved for 3.1 as I'm sure plenty of folks will want to use their Google account as their Civi login.