The last You're Next poster we saw was of the normal variety. Very well done, showcased the general plot of the movie in an entertaining fashion.
The You're Next posters released today? Well they drive home how scary and creepy this movie might be.
Instead of releasing a single poster to the media, the team behind You're Next instead sent individual posters to select websites with a short (somewhat threatening) email.
Ryan of ShockTillYouDrop received an email saying "You've been chosen. The Animals are on the Hunt. And Ryan... #You're Next" with the following one-sheet attached.