I'm convinced it was created by Dharma and not The Others. Team of scientists gathered from all around the world creating it seems like a lot better explanation than an ancient egyptian curse or something. It seems more like a rain cloud than smoke actually, it has electricity in it. Maybe Dharma just made a scary looking cloud thing that makes noises as a scare tactic for The Hostiles or something. And it could be summoned from Horace's house. Maybe the magnetic energy on the island messed it up and now it has a mind of its own? Or maybe Jacob's Nemesis possesed it? It seems to get angry when the island has newcomers, and we know Jacob's Nemesis doesn't like the idea of new people. I doubt the Dharma folks would be able to think of and build the sonic weapon fence before it had time to get them.
Any one have any ideas?