I like that they chose to portray the feisty side of Jacob.
'Like dude where the hell do you're going with THAT, c'mere'
So I'm guessing if you went through the entire series and took note of all the times smokey has stopped short of killing someone, he was considering using them to kill Jacob. This includes Locke and Ekco, although it also means he was considering Juliet at some point :/
It also seems like Jacob knows he has a job to do but nevertheless feels some compassion for the MiB. If we're trusting what the guy said to kate last episode, it seems he may have wound up as the big bad wolf after going through 'growing pains'.
hmmmm. show is getting kind of magical, not sure if I like that.