Most RPG's do not start with a social contract or, when they do, it's an implied social contract. We should consider the PCs in an RPG as actually examples of hyper-individualism that exist completely outside the social contract and that can in fact bend the social contract to their own personal whims (even at extremely low levels). This is probably why player logic is often schizophrenic to the sociocultural logic of the game world whether created by the GM/ST/DM or the game itself.
Starting with an actual contract or direct explication of the social contract of the game world is actually something I'll have to ponder.
This isn't to disagree with Setherick's post, but it brings up a thought of mine on the subject of gaming and how I feel it should be done.
I think the 'social contract' that is present is the one between the players and GM, and not the characters in the game world. The contract as I see it is a shared contribution, where all contributions are deemed of similar worth, for the mutual enjoyment of all parties at the table.
Granted, there are many examples of individual gamers who don't share this view, and game solely for their own enjoyment to the exclusion of others. I had to ask one guy who played in a game of mine to leave because he was disruptive to the environment at the table by the actions of his character.
This isn't to say that characters cannot have divergent motivations or interests, but that the players game with respect to all at the table first, and to their characters second. Setherick makes a good point about the hyper-individualism of characters, and I see this as stemming from an inability to become immersed in a world that is too alien for the player to understand. While an author has the benefit of being able to sit back and review and tweak theirs characters' interactions with the world, a player at a table is required to be more spontaneous. This is challenging at the best of times, but even more so when confronted with situations that significantly impact the players' perceived enjoyment of the game by impact on their character.
I have had some characters that I have been very attached to, and others that I could care less what happens to them. Which one do I role-play better? I don't know. I just try to temper my actions at the table with the other players in mind, so that I don't 'ruin' the game for them, and ultimately myself.