Thanks to Sledgeweb for this excellent image and interesting thoughts on Smokey
Smokey returns in Episode 3x15, "Left Behind". This time, Smokey is chasing after Kate and Juliet. In an encounter with the two, Smokey does something we really haven't seen to date. He flashes bright lights in Juliet's face. This seems different than the scanning we saw with Eko.
Also, when Smokey appears at the fence, we see Smokey emerge from several pieces that join together to form one big smokey. When Smokey runs away, he appears to break into two pieces.
Interestingly, as Smokey approaches the fence, there are three large "heads" that are very noticeable. Could this be confirmation that Smokey is indeed the "Cerberus" mentioned on the Blast Door Map? Is it possible that Smokey is comprised of three separate entities that are capable of joining together, or working independently. Could this explain why sometimes we hear the clackety-clak noises of a roller coaster when Smokey appears, and sometimes we don't?