If you operate a site or service and want to accept identity from large third parties, you encounter a bewildering array of implementations. Some are fairly proprietary, such as Facebook. Others, such as Google, are based on a standard but with a twist. New ones come along, such as Twitter, and present their own versions. This makes building them all a real resource challenge. On top of that there is a real possibility of getting it wrong and creating a usability or worse yet a security probl...
