For example I just watched Dark Skies for the first time. The name conjures up imagery of UFOs blacking out the sky, dark thunder storms, and/or and all out war from above. While the movie did involve aliens, and tons of conspiracies related to aliens, abductions, and UFOs, there was not a single UFO in the film. There wasn't even a single shot of the sky really. It also wasn't dark, being fairly well lit for like, 95% of the film.
Overall it wasn't a bad movie, not great, kind of a mish-mash of things that had been done, but well paced and just mysterious enough to keep the viewer’s interest. However, I also feel like it probably would have gotten another half a star if it had a more accurately named.
Another example of this is Silent Predators, a movie in which the main threat is anything but silent. The main threat, while a predator, is also to small to predate human. It, or rather they, are several aggressive hybrid rattlesnakes, that were, until recently hibernating. The main plot being that you hear the snake rattle, then it bites you, and you die.
Come on guys. Many classic horror movies were named by friends of the director who'd get drunk and watch the film from dusk to dawn, when hung-over they'd called the director and mumbled a name into the phone. Still, it was more accurate then the examples above.
Which isn't to say that there aren't some well named horror movies recently, Sharknado comes to mind. Very descriptive of the small part of the movie I saw, sharks flying through the air, riding a vortex!