There was some discussion about the Internet last week on dark fiction, its definition and boundaries. Dark fiction, especially dark fantasy and dark urban fantasy, is mostly defined in the marketplace by publishers. There's an idea, a valid one, that folks likes their urban fantasy dark. Sometimes, I have trouble figuring out what makes such work dark. To me, this means dark themes left in the wake of grim plot events; perhaps to other publishers it means that the whole story happens at night.
For instance, I've never heard George RR Martin's work called dark in marketing copy, but he tortures his characters so violently and permanently, I fail to see how it could be considered anything but. He eloquently deprives each character of that which they most covet (for instance, a bastard loses his father, a romantic never finds love, a warrior loses his hand, a rambunctious child loses the use of his legs) leading to an overarching theme best stated as: It's not darkest before dawn, but right before your worst nightmare.
For Electric Spec's purposes, we like our dark themes truly dark. I rarely see stories in my slush that push the boundaries of dark fiction. Usually it has to do with under-developed internal conflict. So many writers fail to discover that which drives their protagonist, what makes him feel alive and who he is, and then steal it within the context of external conflict. If we can identify with the protag in real crisis, then the veil of suspended disbelief starts to fall over our eyes. How the protag strives to get it back makes for the plot events that build themes. This might include horror, macabre, even tragedy, but above all, it requires deprivation. Deprivation, often with permanent consequences, is at the heart of every good dark story.