eric.bell makes a good point. Many authors we hold on pedestals today were writing commercial fiction. Dickens was mentioned earlier, and he was paid for each word he wrote. Not only was he writing to sell, but he was embellishing for the sake of money, not because it would enhance his writing. I'm not saying that Dickens was a bad writer or that King is a good one, but it's something to consider.
I have enjoyed a few King movies, because to me he is a good story teller, especially for the screen. But his writing style leaves a lot to be desired. Maybe he's just working with the wrong form?
About the debate on the rules of writing, I think both sides have a point. I don't you can give a set of rules and always follow them. If that were the case you could just write a computer program to follow these rules and randomly generate the details. But then we would lose the human element of literature, and that is what makes it touch our hearts and our minds.
That said, I looked over Twain's guidelines, and though I wouldn't sit down with a manuscript and check it to the list, I don't think I would find a reason to break any of those guidelines.

