Actually, the biggest difference between Diary and the other two films you mentioned, is that with Diary it's actually shot by a student who's first and foremost priority is to document the events. With Cloverfield (which I have not seen, only speculating) and Blair Witch, it was survival first, shoot second. Here, it's shoot first, survival second. Therefore there is no shaky cam. No blurry out of focused shots. When his friends are in trouble, he doesn't put down the camera to help. Instead he keeps a steady shot of what's going on.