Why hasn’t OpenID taken over the world?
OpenID simply stands no chance. It is like saying to people, “Hey, I notice you have a lot of keys on your keyring. Wouldn’t it be more convenient if you could unify them all so you wouldn’t have to carry all those keys? (sounding pretty okay here so far…) All right, here, instead of using those keys, you should take this extremely convoluted and foreign-looking mobile phone, into which you have to insert all of your keys, type in a special password, and then oh, well, it works on most locks but not all of them, so you’ll only be able to replace some of your keys with it, so now you should carry this new weird mobile phone on your keyring too. Also, it doesn’t work as a phone. And it has other companies’ brand names printed all over it. And it calls one of those companies whenever you use it.”
What’s wrong with OpenID? - Quora