I think for me, whenever I read something that I normally wouldn't, (ie, work categorised as "disturbing") it's out of curiosity. Mostly, I want to see if the person can pull it off.
There're a ton of stories out there with warning tags that are longer than the description, and my first reaction is always a raised eyebrow. Sure, they can write it, but can they write it well, or is it just an "UNF UNF UNF HE CUM ON HER FACE N STRANGLED HER" sort of fic?
Case in point, the story I joined this site to post has been up less than a week and it has over 300 hits and one review. I'm not complaining, since I'm writing primarily for myself here, but I can't help but wonder how many of those hits are a result of someone looking for, say, the BDSM that's promised in further chapters as opposed to an actual story. I guess we'll see.
As far as reviewing goes, I also see a lot of stories out there with an immense number of hits vs reviews. It's true that the more controversial the subject matter, the more likely it is to spark a reaction of any sort. I've even seen reviews where people review it specifically to say "I don't normally read this. It's not the sort of thing I'm into", as if they're worried someone is going to think they're a horrible, horrible deviant. In general, I think if you take the time to read something, you should drop some sort of review. Even if it's just a few words.
Also, Stephen King? I keep buying his books no matter what people say. I actually bought Duma Key the other day at the bookstore, and the lady at the cash register sort of raised an eyebrow and curled her lip a little at it. I went, "That's right, I read it! He has more of my hard-earned cash!" I guess it's popular these days to hate on the guy because he's talented, has a ton of money, and, admittedly, has written a few stinkers. (From a Buick 8 springs to mind . . . )