There's probably something in the facebook API in the developers section that will tell you how to go about doing that.
to do so you need to implement the facebook api. I think on unityprefabs or the unity asset store someone sold such an addon
graph.facebook.com facebook.com/developers u can learn here https://graph.facebook.com/me?acess_token=1232..... (login user information as json data)
thanks, now I am work on it, The csharp SDK uses System.Web; reference that doesn't exist on Unity3d. :S