Is MIB responsible for turning candidates to the dark side or for getting them killed?
Ben told Locke the purge was not his idea. It was their leader's. (Widmore) Was Widmore getting orders from MIB while thinking he was Jacob? Was the order to kill baby Alex comiong from MIB posing as Jacob?
That might explain him coming back to the island to redeem himself. Maybe we'll see Jacob visiting Widmore off island just before visiting Hurley.
Anyway, the purge is a pretty good way to kill lots of candidates. "I'm going to finish what I started"