I think the best comparison for the old school facebook wall is laughing or talking really loud at a cocktail party. It’s talking to one person to project an image of yourself to everyone else in the room. That’s definitely a conscious decision people make - am I standing in the corner of the room not taking to anyone and doing my own thing (in which case your profile might have a lot of info on it but very few wall posts) or I am a talker and someone could look at my wall to wall with other people and see me chatting away.
A couple of years ago, I remarked to my good friend Jyot that I didn’t understand where in the realm of social interaction the Facebook wall fit. This morning Jyot got back to me with the above analogy, which works perfectly for random messages that people write on your wall (as opposed to them responding to something you said or posted). Well put Jyot.
