My thoughts on Lost are that Jacob is actually a time traveller from the future. I believe this is substantiated by the fact that he appears to all the cast at differing times in their lives but Jacob is always the same age. Jacob is playing God with peoples lives,we know he has special abilities from Richard saying that Jacob made him always stay the same age. I think we have yet to find out what Ben's special abilities will be, because as a child he was saved after Sayid shot him and Richard took him saying that he would never be the same. I think the island is a time capsule with portals to different time zones, which is why the island does not show up on the radars, that Jacob has created, he brings people to the island so that he can play with their lives and monitor their reactions to situations. But I think he has "elders" from the future who believe he should not be doing this and is interfering in history and therefore they have sent someone back to stop him, the person who has taken over John Lockes body.