FB/OpenSocial development in CI - How to do authentication & user management

[eluser]taewoo[/eluser]
Well, ok, maybe this is more of a statement as well as a question.

I have been using FreakAuth for a while now. It's a bit complicated and large, but very extensive and very useful. But if you're trying to build a social media site that can benefit a lot from integrating into Facebook or OpenSocial, it's sorta useless in a sense that it assumes that all your users are going to submit their username/password/email. If the user had the opportunity to login with their existing accounts on other sites (for example, RPXNow or Gigya Socializr) as WELL as having a choice to register/login with traditional methods, it might reduce the bounce rate and make your site more "sticky".

Wouldn't it be great if there was an authentication system that can interact/do authentication with these social sites? Is there such already?

PS: I'm not talking about doing FB/OpenSocial APP development.. I'm talking about developing a site that TAPS into these social site features (such as publishing to their feeds or what not)