Surprisingly enjoyed this. A little bit.
Katie and he sister Kristi are just children in this one, and we figure out by the end the reason that this "paranormal activity" is occurring. They live with their mother and her boyfriend who is an amateur cinematographer. He decides he's going to set cameras around the house to capture things that happen in the middle of the night. When things start to get serious, he tells his wife, who doesn't believe it at first, but when she sees for herself, she moves them all to her mom's house.
While it's still not a "scary" movie, it still gives you chills and might make you jump a couple times, so it's satisfying enough. It's also better than the second one. I actually can't decide if I like the first one better than this one or not. There were more characters in this one, which I liked. The same thing happened in the first and third which was that the ending was the only freaky part. Paranormal Activity does this thing where nothing really happens until the end.
I don't know what it is with people in scary movies. The first sign that my house was haunted, I would be moving my family out of there at least. If I wanted to stick around and investigate, I would leave my family out of it. Especially, if there was some entity talking to my daughter. Dennis (played by Christopher Smith) sees his daughter talking to turns out to obviously be a ghost, but he just lets it continue. I think he was supposed to be like "too obsessed" with his videos and all the crazy stuff that was happening to care much about anything else, but he didn't show signs of being obsessed to almost the end of the movie.
Not to mention, they left the other daughter at home with one of his friends, knowing this stuff was going on, and that's when the movie finally takes off. I'm surprised they even took this franchise as far as they did. I think four movies is 3 too many, and if they make a 5th one, god help us. I will see the fourth one shortly, just because I've already gone this far. But, I guess this 'Paranormal Activity 3' would be a good movie to watch if you don't like really scary movies, but you want a little suspense. I guess the same goes for all of the Paranormal Activity films.