I like the theory that Ben could see and hear Jacob until Locke arrived on the island. I think Ben expected Locke to be able to see and hear him too and then was happy when he couldn't. But then, Locke heard him and this angered Ben. I think if Locke would've walked in and seen Jacob right away Ben's plan was to kill him. That is why Alex gave Locke the gun. Knowing if Locke had the same powers as Ben, Ben would kill him. I think if Locke had walked out and not heard 'help me' then Ben would've been very pleased and taken him back to camp yada yada yada. Or maybe killed him anyway because everyone is looking to Locke as a leader, when he beat up Mikhail, Ben said 'Tom!' 'Richard!' and they ignored him. Ben is losing his leadership to Locke. Why would Jacob ask for help though if he is so powerful? Also, smokey has been inside and outside the fence so how is it that the sonic fence contains him or keeps him out?? Unless it goes through it when it is off or has to go under it from certain places.