So this is the first time I have ever written a theory, so I apologize ahead of time if I am unclear on what I am trying to say :-D.
I have been thinking about this theory for a while. A lot of people connect "Lost" with a game, especially considering all of the references to Backgammon. I was discussing this with one of my friends, who then referred me to the game "Go". I looked up the rules and strategies of "Go" and was AMAZED at the connections I could make between it and "Lost". In the summary of connections I notice, I view the "stones" as past a present candidates, and the "players" as Jacob and MIB. Here are the connections I noticed:
1. A game between two players placing stones on the points of a grid, one of the players uses white stones, the other black.
2. The grid has 361 points (candidates), the black player gets the extra odd stone because that player goes first (maybe Claire's baby?).
3. Placing stones close together helps them support each other and avoid capture (Live together, die alone).
4. Rules state that "suicide" is prohibited, UNLESS, used in a way that will allow the capture of an opponent's stone.
5. A group of stones can have a status of "Alive", "Dead", or "Unsettled."
6. There is an emphasis on "Eyes" (A repeated theme in Lost). An eye is an empty point that is surrounded by friendly stones and where the opponent can never play due to the suicide rule (Places such as the temple?)
7. The use of time control.
8. The most basic capturing technique is a "ladder" (Jacob's ladder came to my mind). This consist of a player FORCING an opponent into a zigzag pattern in which they cannot avoid capture. This would be Jacob's technique, because he forces people's decisions, and to (and back to) the Island. This would mean that Jacob, along with MIB, is not neccessarily on the survivor's side either.
9. Another capturing technique is the "snapback." In a snapback, one player allows a single stone to be captured, then immediately plays on the point formerly occupied by that stone. I Connected this with MIB, taking over the bodies of people who have died, Locke, Christian, etc.
10. One of the most important skills of the strongest players is the ability to "read ahead" (Desmond).
11. "Tsumegos" are life and death problems, often used as practice materials to train players how to read ahead. (Desmond trying to save Charlie).
12. The use of "Sacrifice", allowing a group to die in order to carry out a play, or plan, in a more important area. (Looked at this in a few ways, Nadia dying, allowing Sayid to come back to the Island, and then sacrificing himself to save the rest of the survivors. Charlie sacrificing himself to try to save the others. Micheal sacrificing himself. etc.
13. (This one is a stretch, but still something I noticed) The ranking system used to compare players is the "Elo rating system" (Eloise!) One of the two grades used is a "Dan" grade.
14. Finally, whereas Backgammon is a game of "Man-vs-Fate", Go has been described as a game of "Man-vs-Self". (Lost can be seen in both ways, but considering how most, if not all, of the players are on continued paths of change, redemption, and atonement, I think the latter applies more.
So basically my theory is that Lost has some connection to the game Go. Maybe Jacob was telling the truth when he said that he and MIB disagree on human nature and man's corruptability. Maybe they are using a game as a way to set up rules on how to "play out" their disagreement. Obviously, there is A LOT this does not explain, but I hope you enjoy the theory anyway!