Well, I agree that there may be something between Ben and Alpert, but Ben is such a good actor, on the island that is, he is so convincing. When Locke asked why he was playing him, Ben said "and where would you get an idea like that?" So Ben knows he is at odds with some people, maybe Alpert, or, it was all part of an even longer con. Somehow, i think it's the latter, I mean Alpert seems to know everything, he seems to be a right hand, and he was integral in getting Juliette to the island, so why now would he be against the fertility. It's a long con for sure.... I bet Ben is setting Locke up to kill Jacob, so he can have all of the power.. who knows