Historically, a social game is one that you played with friends so that you could socialise while you were playing. Board games, card games, RPGs all involve having a group of people in the same room and even if you took your gaming extremely seriously, there would be time to chat between rounds.
The social part of MMOs is grouping. Again, you’re tackling the game with a bunch of other people and if they are also friends then you can chat while you kill mobs together. Even if you aren’t grouped up, an evening in the MMO for a social player means chatting to your mates via various text channels while you pursue other goals in game. But in a facebook-type social game, you interact with people without talking to them at all. Just send someone a virtual cow along with a virtual poke and maybe they’ll respond later.
So I wonder, how social can any game really be if you don’t talk to anyone? Are we heading towards the ironic situation where Bartle-type social players dislike ‘social games’ because they aren’t social enough and you can’t really get to know the people you are playing with?