So, I just wrote and handed in a vampire novel.
What bit me?
(Author pauses to allow the shower of rotten tomatoes to subside ...)
Vampires in fiction are a cliche. But a cliche isn't necessarily a bad idea; it's actually a good idea that has been overused.
Here in the real world, we don't see a lot of blood-sucking species. I'll grant you leeches and desdemontid bats. But these are highly specialized parasites. Blood is actually a rather crap food source in many ways: it's high in protein, really low in fatty acids and sugar, and vampire bats need to consume a third of their body weight in blood per day just to stay alive. It's no accident that vampire bats and leeches usually pick on host species that are several orders of magnitude larger than the haemophage! A hypothetical humanoid (and human-sized, mammalian, and human-predating) fanged fiend would have to leave a horrendous trail of drained corpses behind it—just one obligate humanoid haemophage would be enough to increase the UK homicide rate by around 50-70%.
Hence the first line of "The Rhesus Chart" (which is due out in July 2014):
"Don't be silly, Bob," said Mo: "Everybody knows vampires don't exist."
So what are vampires good for?
Leaving aside a whole bunch of different mythological tap-roots, some of which are quite interesting in their own right, the modern western interpretation of the vampire is largely the fault of Bram Stoker (although he, in turn, was working in a literary tradition with notable antecedents such as Varney the Vampire).
The interesting thing about vampires in fiction is what they're used to represent. Vampires are the talkative reflection of our fears; unlike horde-shambling zombies they're singular entities, intelligent and outwardly handsome, the exterior shell concealing festering horrors within. And the nature of the horrors in question changes with time. Back in Stoker's hey-day, the fear of contagion, of the degeneration and insanity that went with syphilis, was clear: so was the clash of uptight Victorian public morality and private lascivious debauchery that went with it. (It's no accident that Vampirism-as-AIDS was the big metaphor of the 1980s: blood, sex, and death are deeply intertwingled in our collective id.)
More recently, we have a whole bunch of other vampire metaphors. There's the untrammeled greed angle, the psychopathic serial killer angle, the sexual predator. Vampires are rapists, non-consensual sadists and torturers, serial killers. They are, above all, parasites and sociopaths—you can't be a vampire, a successful apex predator upon people, and feel much empathy for your prey.
So what do we make of that sub-species of vampire that fucks its food?
One of the weirder twists in the development of a sub-genre happened some time in the early 1990s, with the advent of the paranormal romance. In retrospect it's fairly obvious what they're for; they allow the reader to vicariously explore emotional aspects of BDSM without the troublesome need to find a partner with a roll of duct tape and a flogger who also understands the need for safe words. (This may also be a side-effect of changing gender/power relationships in society at large causing confusion, uncertainty, or dissatisfaction with traditional power roles: don't tell the Pope. Ahem. There's a really complex knot of issues here, including the implications of the demographic transition for human interpersonal and familial relationships, that is probably food for several PhD theses.)
Paranormal romance turned out to be a huge growth industry, inflating rapidly until it's a genre in its own right, and one that outsells traditional SF by a considerable margin. This is entirely reasonable if you view fiction as a play-tool we use to explore the emotional or intellectual scope of ideas that intrigue or disturb us. But that's not where I went with "The Rhesus Chart"; I had an existing framework (yes, it's the fifth Laundry Files novel) and wanted to explore a different issue—the existential dilemma that a non-psychopath might experience if they suddenly learned that in order to survive, they need to kill at least two people a year.
Blood, death, rape, disease, sex, and greed are a far cry from the biology of haemophagic carnivores. We've come a long way from Transylvania, and I suspect there are many more miles left in this not-obviously-tired genre trope.