The more I think about, the more I think that smokey doesn't appear in human form. We've never actually seen smokey turn from smokey to something else. I think when we all saw Eko's brother, and then saw Eko get killed by smokey, we just assumed that they were one in the same. Especially after his "brother" said "why do you think I'm your brother?" or something like that. I think Jacob is controlling/making the "ghost people", and smokey is something else that he controls. I would have said that smokey was created by the DARMA folks, but that was a creepy old looking door that Ben went through in his house to sic smokey on the freighter guys.