I believe it is possible to run a truly scary game at a roleplaying convention irrespective of the environment.
I've been on about this for a while now, so I think it's time to try and tie in the things I've written about this, as a first step in trying to actually put together a game which delivers on this aspiration.
The principle framework will focus on:
-Player buy-in and empathy (through a degree of shared narration)
-Visual and audio aids (not in a major way - just to cover learning bases)
-GM ground rules and time out zones
-Shared Character development
-Identifiable sitations and choices
-Distance closing techniques
-Disruptive player techniques
-Increasing the stakes with (almost) every successive scene
I will attempt to detail my thinking, and the way I tackle this as I move toward the Experimental Paradigm Of Contemporary Horror (EPOCH).