So what's up with Smokey? One minute he's all only become dead people, next he's only become dead people on the Island, then he's become anyone. So in my opinion Smokey can only fully become a person (harness their memories...) if they are dead on the Island (Locke, MIB...), he can appear as an image of a person whether they are dead or alive on or off the Island. This would explain Walt visions, Isabella and so on.
What do you think?