In the episode where John Locke gets shot by Ben, and where earlier he hears Jacob asking him for help, if you freeze the picture where the face of Jacob is partially and furtively shown, I was very surprised with the resemblance.
At the end of this finale I now think it is true.
So who is Jacob?
I wonder if the makers of Lost have an alternative script, but the treatment of the John Locke character reminded me of Gilbert Gosseyn in The world of Null-A by AE Van Vogt, where in his books, he explores general semantics and its possible applications in organizing human life. The hero Gosseyn, like John Locke is looking for answers about his world, finds out also like John Locke that in fact he is the architect of his world.
In other words:
John Locke = Jeremy Bantham = Jacob, and yes the flashing face in the shadows of the person sitting on the chair inside the haunted house is none but that of John Locke / Jeremy Bantham...