Smokey Picks on the Vulnerable by Mystery Scribe

I think Smokey looks for someone vulnerable who he can influence. He scanned Locke and even though Locke had grown so much on the Island, he still carried his disappointing off-island life with him, always just below the surface. Eko, when scanned, wasn't weak at all. He had a very strong will, so Smokey killed him rather than take the chance that of a strong-willed potential adversary being alive on the Island. He used Ben's grief over Alex's death and his embarrassment over Jacob's snubs to convince Ben to kill Jacob.

Why didn't Dogen want Sawyer to leave the Temple, yet he let Kate and Jin go? I think it's because Sawyer is very vulnerable right now. He's ripe for the picking. I think Smokey will try to get him on his side and will succeed because of Sawyer's grief and self loathing.
Smokey, in short, takes advantage of vulnerable people who are searching for redemption. He gives them a task that furthers MIB's agenda. I think we'll see a task that Sawyer agrees to do on Smokey's behalf before the end of Lost.