When I last used Facebook authentication, it provided it's 'Facebook Connect' protocol which wasn't necessarily implementing the open source OAuth protocol but now they say that they are using OAuth 2.0 protocol. When did this take effect? and will Facebook Connect be disbanded?
They added OAuth support around April of 2010 to make it easier for third-party developers to work with their site. IMHO it was a very good move on their part.
While they haven't (AFAIK) announced any plans to discontinue Facebook Connect, they are moving forward more aggressively with OAuth and their Graph API as the new way to get things done.
Basically, this is par for the course with Facebook's dev team. They make one thing, get everyone to use it, then realize they messed up and start over, leaving the old system in place for a very long time. So you're probably safe with Facebook Connect for a while, but it's not the route I'd go if I was starting on a new app that was going to integrate with Facebook.
April 21, 2010. See: The Next Evolution of Facebook Platform
We've also made it much easier to integrate with Facebook by using a simplified, standards-based method for authentication and authorization.We've adopted OAuth 2.0, a standard we've co-authored with the open community, including representatives from Google, Twitter, Yahoo, and others.