But didn't Ben tell Jacob something to the effect that he couldn't hear Locke if Jacob kept talking... I Was under the impression that Ben could hear Locke, to the exclusion of all else?
I was thinking this morning that when Locke said he had looked into the eye of the island and what he saw was beautiful... (maybe Locke didn't understand it completely, but) Locke was actually looking into Jacob's eye? That's why Locke saw something beautiful (and later told Eko,"that's not what I saw" and why Locke told Jack that Locke would be okay if Jack would let him go when Locke was dragged away by Smokey). Jacob had connected with someone who could help him, and Ben knows nothing about this. Ben might sense something is different with Jacob and that there is something special with Locke. Which would lead to Frogmeister's excellent idea of of why Ben was so insistant that Locke kill his father.

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`Dear, dear! How queer everything is to-day! And yesterday things went on just as usual. I wonder if I've been changed in the night? Let me think: was I the same when I got up this morning? I almost think I can remember feeling a little different. But if I'm not the same, the next question is, Who in the world am I? Ah, that's the great puzzle!'

-- Alice, from “Alice’s Adventure’s in Wonderland”