I have a request for implementing a login system using local credentials + openId + facebook-connect.
So a user could sign up/sign in using any of the 3 possibilities.
I think that allowing OpenId AND facebook connect adds some flexibility, but in other hand adds some restrictions since you have to integrate all different logic and make existing differences transparent for users.
What do you think? Any good reference for managing federated login using both external mechanisms? Any well known site doing it right now?
RPX lives to take care of the complexity for you.
But if you've made your system able to do any two of the three auth methods mentioned, adding the third isn't that hard. You've probably already got all the necessary abstractions and workflow elements done.
As for who's doing it... seems like a fair portion of the OpenID-enabled sites I see these days have Facebook Connect too. I'm not sure which count as well-known... I guess you could browse RPX's customer list.