Originally Posted by VidaRed

the monster is the course corrector....it sees people future and analysis them and if it thinks that there thinking will change or they will alter things which weren't supposed to be done or something like that then it kills them like it killed eko because his personality had changed while on the island and most he would have acted differently that what he was detained for...eg like he was a drug lord off the island and on the island he became a religious and spiritual and that would have altered his thinking so the smoke monster killed him.