Ones who encounter the smoke monster are the ones who become "infected"
Rousseau's team in the 70's
Claire, in the cabin
Sayid, through the spring
Christian? I agree with the theories that his body became "infected" and he's not MIB
Eko, he likely would have had he survived
Ben on several occasions interacted with the smoke. None more than when he was "judged" outside of the statue.
It would seem likely he would have got it at this point, should be interesting to see when he along with Ilana, Frank and sun arrive at the temple. Perhaps he fails the test as well.
Perhaps we'll see Ben, Claire, and Sayid ally together in some way.