This unnecessary follow-up to Paranormal Activity re-treads the original formula with a weak tie-in and none of the raw suspense. The underlying story in the first film was more plausible and claustrophobic. In this one there's no consistency and no one knows what's going on or why.
The POV device doesn't work as well because they are always conveniently filming themselves for no reason. The characters (all annoying and not remotely credible) seem to forget sometimes that the story is told through POV, since they never really give credence to the tapes when something happens. There is also way more asinine exposition (an hour goes by before anything substantive even happens). The story in the first film was simple and so it worked. This just plays to our sensibilities by putting a baby and a dog in harm's way while doing nothing to advance the story.
This movie tries desperately to weave itself into the framework of its predecessor to the detriment of both. Paranormal Activity 2 uses all the same visual gags as the first, but they happen out of place and absent of story. In the end the camera just starts shaking uncontrollably and the lights go in and out. It makes you nostalgic for the no-budget feel of the first film.
Paranormal Activity 2 illustrates the same lesson we learned from Blair Witch 2: Amateur filmmakers trying to be professional are much more capable than professionals trying to look amateur.