There's been some interesting posts about the "smoke monster," but I am not 100% convinced there is only one smoke monster. It's like a line from season 1 when someone said "Sawyer killed the polar bear." I believe it was Sayid who responded "No, Sawyer killed A polar bear."
At this point I'm not totally convinced that every time we've seen black smoke, it's been MIB in that form. Maybe Jacob can become a smoke monster, maybe there are others too.
I first thought of this when Ilana said Flocke was stuck. Maybe these entities are wandering around as smoke monsters untilt hey take over a body. Once they take over a body, they can go back and forth between the body and monster form, but can not take on a new body.
The other thing that got me thinking about this was Dogen's comments to Jack. He suspected Sayid had been claimed, and also that Claire had been. Meanwhile Locke had been claimed. He might not know about Locke, but he still mentions Claire. Why would he be worried about Sayid being claimed if he Claire already is, unless there are multiple entities to claim them.
I am not saying there are for sure multiple smokies, but I also am not convinved there is only one.