Seems the ball has really started rolling on this one. According to O’Reilly (http://radar.oreilly.com/archives/2007/02/aol_supports_op.html) AOL has started supporting OpenID for AIM users. It’s only a matter of time before Google’s on this one.
I had a look at the OpenID specs to get a decent understanding of exactly what the protocol was about. There is nothing there that can really be hijacked and made proprietary. Anyone who has worked on web applications such as portals whose services need to rely on a shared identity will instantly recognize the pattern in a collaboration diagram. I slapped one of these together for myself just as a matter of interest (a picture tells a thousand words). I’ll put up a post this weekend explaining the interaction.
The interesting thing here is going to be how exactly the scheme is going to be promoted/adopted. OpenID requires that every identity corresponds to a URL – at present AOL/MSN/Google accounts all correspond to an email address. Watch this space.