After looking at the docs it doesn't appear to be incredibly hard. I think the most non-trivial thing would be integrating with the current site sign-on. Issue

After looking at the docs it doesn't appear to be incredibly hard. I think the most non-trivial thing would be integrating with the current site sign-on. Issues such as an existing users that decide to sign on with facebook (which is linked to a different e-mail address) could become a problem on the backend.