Ben plays for team MIB by Crabsy

I've seen a lot of theories that Ben is in fact conning MIB, but I'd like to offer a counter to this and suggest that Ben has in fact turned bad, or at least recommitted himself to being bad.

Recall to the season 5 finale when Ben kills Jacob. Ben was upset that after years of following Jacob's orders, Jacob continued to ignore him. However, he had no problems revealing himself to Locke in the cabin. This prompted the following exchange: "What was it that was so wrong with me? What about me?". "What about you?" Ben snaps and proceeds to kill Jacob.

WTDF has a similar occurrence in the barracks. Widemore appears and he says to Ben that Jacob invited him to the island. He then tells Ben that following the destruction of his freighter, Jacob came to him and explained everything he needed to know. Now, if Ben was upset when Jacob communicated with Locke, how do you suppose Ben felt about this revelation? Jacob not only showed his face to Widemore, but also explained everything he needed to know about the Island, all of which had to happen AFTER Widemore had given the order to kill Alex.

I believe this conversation in the barracks that Jacob essentially confided in Ben's sworn enemy completely cracked him, much in the same way he did in the season 5 finale. Shortly after this exchange, Ben has a conversation with MIB, wants to watch Widemore die, asks if there are any more to kill, etc...

Also, this idea that man is evil, corrupt, will destroy, etc... needs to be realized on the island by somebody other than the MIB. It can't be an island full of great people willing to do the right thing and MIB. That's too one sided for LOST. If man is so corruptible, why doesn't MIB have any followers? Ben is the ultimate example of man's capacity to corrupt and manipulate. He's playing for team MIB.