Everybody is speculating on who Wallace is. Here's my answer to that question. Wallace is the one who Jacob is trying to get back to the island. His name was crossed out because he was thought to have left the island and therefore unimportant anymore. That's the reason Shepard and the other candidates appear in bolder lettering. Their names were crossed out and had to be rewritten when they returned to the island. That's what made their reappearance such a big game changing event to the island. MIB thought he had possession of the only candidate he would need to spoil Jacob's plan in the person of Locke locked down. Now who has left the island and not returned? Charles Widmore is trying his damnedest to get back to where he once belonged. I think that Widmore is not his real surname. If you will remember, Ben had lots of different Ids stashed away with different names when he left the island. I think Widmore is ! an alias. And I think that the label "Jones" on his stolen uniform was a clue as to this being so. Alias, as in Alias Smith & Jones. Widmore is the Wallace who is returning to the island. His true name has been Wallace all along. Jacob knows that because he chose him as a candidate once upon a time.