Amnesia reminds me: another problem with horror games is that "game" elements are at odds with "horror" elements. I played the demo for Amnesia and the atmosphere broke as soon as I picked up a chair, because the next thing I thought was "If I can pick up chairs, can I stack them?" and there was nothing to stop me from lugging it to the next chair, which looked very silly and distracted from the feeling the game was trying to impart... and the answer turned out to be yes, you can stack chairs.

You know you start that level having apparently fallen through a hole from an upper floor? I wanted to know what was up there, so I went around and gathered all the chairs in the level to make a big rickety chair stack I could sort of awkwardly jump up. I guess they knew someone would do that, because there was a cheeky message scrawled on the wall up there. But it's completely impossible to be scared by a game after you've spent twenty minutes faffing around with physics objects.