It's one thing to have a movie spoiled by reading about it on a Web site; I chose to go there and I chose to read the spoilers.
It's quite another thing to have a movie spoiled because a coworker can't be bothered to walk five feet to the other girl's cubicle. And it's yet another thing when she gives me the "ugh, whatever" look when I call her on it. It's the second time I've spoken up like this with her.
They should call it the "Sixth Sense" rule of office ettiquette: If you're discussing the twist ending of a recently released movie or TV show, for God's sake, keep your voice down!