What does Facebook Login do in MW3 Multiplayer?

I see there is a Facebook Login in the MW3 Multiplayer main menu and I wonder What it actually does.

Will I have to install a Facebook App in my Profile?

If it works as an announcer, can I set who sees my actions and to what extent? For example: I want only my close friends and not my co-workers see my progress. Is that how it works?

And one-nice to have: I see the login is not diverted to a browser but takes place in the client. What is the security situation here?
Can anyone network sniff and see if it is https?

A video was posted last week that describes Modern Warfare 3's Facebook integration. I believe mostly focuses on helping you to find games with your Facebook friends, but I'm not positive on that.