A whole bunch of folks have the same reaction to first-person shooters.
It's funny though.. there's also a sub-section of halo gamer that get's nauseated by watching other folks play, but is fine playing it by themselves.
Those same folks tend to hate those "moving theaters" too (like the Star Wars "ride" at MGM Studios, where the theater itself tilts, lifts, drops, etc).
My buddy is one of those players, but he was fine when we saw Cloverfield together.
Hmm.. one thing about Halo first-person though.. the Camera never leans.. it tilts, rotates, rises and falls, but never leans. I wonder if that has anything to do with minimizing motion sickness?
Quake 1 used to lean a bit when you got nailed by something like a rocket to the head or something. I used to LOVE that effect because it was a little disorienting, mixed with like a red haze. It was cool when running flat-out and taking hits but trying to get to a goal.
Ohh and the point made here about the "looking for a stable position to reference from" is entirely valid, and my sister watched Cloverfield by sliding down in her seat to use the person's head (in front of her) as a reference point. She said she kinda' did it without realizing it, but until she did, she was starting to feel queasy too.
