There is a fair amount of snuff fiction on the web. I don't think most of it is written by homicidal maniacs. Like most BDSM fiction, much of it is horrible, but I did see a usenet story by someone with the pen name "Happy Hangman" or "HappyHangman" that I thought was well done.

As to what it represents, do people into 'general' BDSM want to go back to the pre 1865 South and either be or own real slaves? The idea is repugnant, yet the 'master' and 'slave' tradition is well established in BDSM.
I have a couple of theories about snuff fantasies- one, already mentioned, is that just like BDSM it's about trust and control- the sub trusts someone enough to give up control, the dom is so trusted and you give yourself so completely that you can let him/her do anything, even take your life if they want. (You let somebody tie you up and you are literally putting your life in their hands anyway.) So what is the ultimate in control? Either taking or giving a life- again, in fantasy here. If you really do it not only do you loose a partner with your own rather unique kink, but the government tends to take a rather dim view of it.

I think it's also a way of dealing with death- eroticize it and it becomes more approachable. The association between death and orgasm is already known (one of the French euphemisms for orgasm is 'small death')- orgasm is a way of creating new life, but the only reason for that is because you're going to die. I've also read that there was a myth that men only got so many orgasms, that with each one they ejected some of their 'life force' and when they finished they died.

I wouldn't get to freaked out by fetish unless you think you're actually going to hurt somebody.