Johannes Ernst’s discuses the business ramifications of Yahoo joining the OpenID space:
Instead of being a technical curiosity, web businesses can now assume that the majority of their visitors have an OpenID. Okay, Yahoo and AOL and Blogger and all of the existing implementations don’t add up to more than 50% of internet users, but you can bet that more telcos become OpenID providers for their broadband customers, as Orange showed, and that all major internet portals, Microsoft and Google included, will offer OpenIDs with each of their accounts shortly. (It’s easy for them to do, and they don’t want to lose even one of their subscribers for the reason that they didn’t add a small bit of code to their site, that, boy, might even benefit them strategically, and not just create competitive parity.) It’s a very safe assumption for web businesses that by the time they can do anything about OpenID, regardless how fast they move, more than 50% of their visitors will have an OpenID, and Yahoo!’s move yesterday made that a virtual certainty.