Why Smhristian tried to kill Jack.
Smokey has claimed responsibility for leading Jack through the jungle as Christian in season 1. So here's what I'm thinking:
Smokey took Locke's appearance because it allowed him to earn Ben's trust and coerce Ben into killing Jacob. Well, when he took Christian's appearance, he knew he wouldn't be able to accomplish such a feat because Jack would of course know something was whacky. So I think he wanted to take form of one of the 815ers and use it to gain influence with the rest of them. And who better than their new apparent leader, Jack? Smokey's not allowed to kill the candidates directly (I don't think we have any proof of that, but it seems implied), but he thinks "maybe I can use the Christian form to cause Jack to have an 'accident' and fall off a cliff. Then people on a forum can refer to me as "Smack." Ah! There's that crazy bald guy, pulling him back up to safety. Hmm, well, I still have plan B, which is to show Jack the empty coffin and really freak him out - maybe he's enough of a sucker that he'll start believing that the island is special and that he's here for a reason."
They got . . . the mustard . . . out!