Good to finally reach at least some level of consensus. Smokey is a vehicle for MIB. Sure, MIB might have gotten more cynic during the 2000 years of being entrapped by Jacob, more willing to do immoral acts. We can forgive Jacob, since he did it out of rage, and didn't actually know what he is doing, but I don't think his brother can. And, while smokey has become a ruthless killer in order to become free again (Rousseau's crew, pilot, Yemi, and now our losties, yet strangely he spared Keamy), he doesn't seem like "evil incarnate" to me.
So either the whole evil thing is all in Jacob's mind, or MIB escaping would involuntarily cause the end of the word, by bringing the "light" outside of the island. MIB never seemed interested in power (unlike Jacob, Ben, Widmore, Locke), he had one goal: to get across the sea, so I don't see him becoming a bloody dictator, maybe more of a "Dr. Manhattan" figure or a loner. His only guilt (before becoming Smokey) is curiosity (OK, he killed his mom, but it wasn't exactly for nothing).