My theory is about christian shepard and the smoke monster.
Now, I have read that people think that christian and the smoke monster are separate beings, which is most likely true.
We know claire is infected, Sayid is infected and all of danielle's team was infected.
What do these people have in common? They all have died and there bodies where on the island. With that said, what actually happened was MIB took over christians corpse, turned it into a zombie, and he has been around the island as christian the infected.Thats would be the reason his body was not found.If MIB has control over these former loved ones and friends, its very easy to manipulate those people that are alive and were close. Just like we saw of claire last week, she died and is now under the smoke monsters control. Its also why she said my father and my friend because christians reanimated body is still on the island and MIB has been using his Body to convince Jack, Claire throughout the series to do certain things such as almost leading jack off the cliff.
To be clear, i think there is only one smoke monster and anything else that appears to be the smoke monster (dead people) are just reanimated bodies under MIB's control.