I was re watching The Brig and heard Ben say something interesting. He is telling Locke how he doesn't think Locke is ready to learn the secrets of the Island because he wasn't "one of us" yet. Ben say to Locke, "When people join us here on this Island, they need to make a gesture of free will, of commitment. That's why you're going to have kill your father." I think the "gesture of free will" seems to be a very Jacob-esque idea (if indeed Jacob is the leader of the free will gang), but I think it's all Ben who asks Locke to kill his father because he knows Locke won't do it.
So this made me think, what might other "Other" leaders have asked people to do in order to be inducted into the group? What if Widmore told Ben he would have to take a leading role in the Purge to secure his place?
And finally, could Jacob's disdain for Ben (if it was, in fact, that) be because of Ben's constant manipulation of people's free will by planting his ideas in their head and making them think it was their own idea?