From what happened to Eko when he saw the monster, it seems like it read his memories in order to judge him, or whatever purpose. However, if the monster can read memories over a frequency, maybe it has gotten into all their heads and mixed up memories. This would explain why characters show up in others' memories, like Jack's dad and Claire's. This would logically explain why there are so many coincidences in characters lives: they are creating false memories by picking up on people from another's memory. Is this close to the truth or not? I don't think this explains Desmond's and Jack's connection and some others...