When Batmanuel finds Ben as a child in the jungle he seems taken aback that he's seen his dead mother. He seems to think he's "special," ...reminiscent of how they're treating Locke.
I think those that can see/communicate with the dead are important to the Natives because of their ability to communicate with Jacob (who I suspect is/was the patriarch of the Black rock ship). They thought Ben was their guy, but they're coming to the conclusion that he's not--Locke is.
BTW...The title, "The Man Behind the Curtain," and Locke's line to Ben, "I think you're the Wizard of Oz" is interesting; it wraps back to the name Ben called himself when he infiltrated the Tailies--"Henry Gale," the name of Dorothy's uncle in the Wizard of Oz.
Also, was Ben's dad played by Uncle Rico?