Has he always been this way? That would be an indicater if he has suddenly quite talking about stuff but if he has always been like this, I think you will have to accept him as he is and that's not chatty.

If you are his friend on Facebook, don't be offended he put something there that he hasn't shared with you. He may just feel better behind the mask of Facebook.

Maybe if you don't push him to talk so much maybe he would start sharing, I doubt it but you might try it. I think you just have someone who's not big on talking. Sorry.