The ghost/killer is essentially a STD.
1. If someone is carrying the ghost and fucks you the ghost goes to you.
2. Once you have the ghost it will follow you and kill you unless...
3. You fuck someone else and give them the ghost before it gets a chance to kill you.
4. The catch if that person doesn't have the chance to fuck someone and get rid of the ghost before the ghost kills them the ghost will then revert back to you and kill you.
5. So, what do you do to make sure the ghost doesn't kill you while also trying to do as little damage to other people as possible?
The downside is that instead of just going for that moral challenge it becomes like a good Buffy episode (but with full frontal male nudity.)
I don't have anything against a movie having a blonde girl getting a bunch of her friends together to slay and oggle naked ghost dudes - but I do feel that the premise of the film is better than that.
Anyway, it is good. But it could have been great, and doesn't manage to be as wonderful as the basic concept.