Apostle83: Why would Esau appear as Jacob to Jack, Kate, Sayid, Sawyer, Hurley, or Locke if none of them had met him on the island?
No, I think it's Jacob himself. And I think Esau has been manipulating Ben all this time to be Jacob's killer since the moment he appeared to him as his mother. He put things into play and use other moments to his advantage to make Ben so bitter towards Jacob that he would be willing to kill Jacob when they finally meet. Jacob might have sense that Ben was a part of Esau's plan and that's why he didn't bother to meet him. When Jacob said "What about you?" to Ben, he meant that he saw Ben as nothing more than a pawn in a chess-game between him and Esau.