After last episode the common assumption was that the Smoke Monster/Flocke/MIB had been behind the infection of Sayid, Claire and other islanders. My theory is that the Man In Black caught the infection. What if he started out as a good guy and friend of Jacob but was infected and became evil?
After Flocke sees the visions of the boy it seems like there is a more powerful force on the island than the Smoke Monster. Maybe the Smoke Monster is not as powerful as he appears.