Mankind has always feared what it cannot understand...

I guess one of the staples of horror films is that the horror in question comes from an unknowable source.

Examples:

• The afterlife (hell, ghosts) or realms of magic.
  
• Space/other dimensions (Aliens, Event Horizon)
• Complex Science/technology (Frankenstein, One Missed Call, Ring)
  
• The ocean depths (Sphere, Cloverfield)
  
• Somewhere that civilized man does not tread (the American South, Europe, the Outback)
• Within the minds of one's fellow man (psychopaths)
• Within the minds of children (nobody knows wtf they're planning)
• Within the minds of clowns
  
• Creating areas of uncertainty and confusion in what was previously well known and everyday to the viewer .i.e. perversions of normal life (Waking up to find nobody has a face/Scissors suddenly killing people)

The horror genre is in need of a boost, so I've been trying to come up with other areas that are mysterious or confusing or incomprehensible to the common cinema-go-er, from which can spawn horrifying things.

It's not been going very well.

This is all I've got sofar:

• Aging - nobody but old people know what it is like to be old but society as a whole seems pretty scared of it. I'm not sure how a physical representation of the fear of aging would manifest. Maybe just a monster that sucks people's youth. Or a killer old person. Scrap that.
  
• The Future - nobody knows what the future will bring and thus it is often scary. Unfortunately, now that I think on it, fear of the future has already been used in stuff like Final Destination and The Ring, where an unspecified doom is placed upon it's characters.

Now that I really think on it, Shakespeare was doing that stuff with Macbeth. Pipped to the post by 400 years. Darn.

Well that was a productive waste of time. The horror genre is exhausted.

Edit: Sorry, one last idea struck me.

• Homosexuals - the gay community becomes violent and rapey towards straight men?

The gay community is an enigma wrapped up in an conundrum to me.

So is the furry community, but they don't have quite the craving for man flesh.