What next, a haunted blog that will kill you if you don't dutifully read every post?!
Byeong-ki Ahn must have thought that all he had to do was include everything that ever scared anyone in the modern Asian horror genre (and a good looking cast) and he'd have a classic on his hands. The first five minutes alone work all the key tropes: scary rain, scary lifts, scary lighting, scary hair.
The trouble here is that two separate story ideas have been badly gelled into one plot. The first, more basic one, is the techno-terror concept of an unpleasantly possessed mobile phone, which was bound to go down well with younger Korean audiences.
The second one is a parable about the scariness of marriage and parenthood, which plays on deeper, more adult psychological fears. The beginning and the end are enjoyable enough, but the mid-section, where there is something of a transition between the two underlying themes, almost lost us.