It's a popular theory that Nemesis= Ol' Smokey. I've got two reasons for agreeing with this.
Firstly, when Benjamin summons Smokey in S4 to attack Keamy's men, Smokey's there pretty damn fast. But, he 'never' appears the second time he does it, but 'Locke' does come out of the jungle. Obviously Nemesis= Locke.
Secondly, when Ben goes to be judged by Smokey, the Nemesis conveniently leaves right as Smokey judges, and comes back just after Smokey leaves.
I think these are both really subtle clues about Smokey's identity. It wouldn't be a stupid idea for Jacob to be fighting against Smokey for control of the Island. Maybe Nemesis adopted his Smokey form to escape the Ring of Ash, until he could break it and leave in full force.
Are there any other clues I haven't noticed? Does anybody disagree?