I have reached an interesting conclusion regarding Joss Whedon's rules of vampirism, created for the Buffyverse.
Now, Whedon's rules are, strangely, both very traditional and rather unorthodox at the same time.
Traditional rules that apply:
Wooden stakes, sunlight, holy water, crosses, hallowed ground, fire and decapitation are all ways to harm/kill a vampire.
The most obvious here is sunlight; merely standing in the shade is enough to protect a Whedon vampire from sunlight damage.
Vampires can and do eat solid food, but gain no sustenance from it.
I'm not sure whether this rule is traditional or an invention of Anne Rice, but Whedon vampires are created when a vampire's victim is forced to drink the vampire's blood after being drained.
Which brings me to what I've been thinking about, what I've been noticing: the amazing inconsistency of how the vampire rules are applied from episode to episode, and situation to situation.
For instance, the above rule on the creation of vampires implies that it should be an extremely rare occurence. However, on many episodes of Buffy, we see her waiting around fresh graves, ready to stake a new vampire that she apparently knows is going to rise simply by the fact that the deceased was killed by a vampire (which also begs the question: how often do people get buried the very day they die? Since it is shown that new vampires rise on the night following their demise).
However, the major inconsistencies emerge regarding the ways in which vampires are slain. For example, sunlight. Now, usually, they are pretty loose with sunlight. As I said, vampires can hang about in the shade, stand strangely close to windows, run around in the sunlight wearing a smoking blanket, drive cars with blacked-out windows (how exactly does Spike see the road?) and have brief contact with sunlight that sends them sizzling towards the shade.
This is where the inconsistencies set in: Whilst the above rules seem to apply most of the time, you will sometimes see vampires burst in to flame and disintegrate immediately on contact with sunlight.
The same applies to fire, but in the opposite direction. Usually any minor contact with fire, from say a burning torch, is enough to snuff out a vamp's eternal life, but in one notable instance, being completely on fire was not enough to kill two vampires, who had time to run outside, break a fire hydrant and extinguish themselves.
Which brings me to the conclusion that I said I had come to:
Joss Whedon's rules of vampirism are an extension of the "red shirt" phenomenon from Star Trek.
All manner of horrible things can befall the major characters week after week after week, but they will withstand it and go on living.
However, the slightest little thing will bring about the demise of an unnamed extra.
So: sunlight, fire, holy water, etc, is enough to cause nasty burns and pained expressions on the faces of Angel, Spike, Drusilla, etc, but are enough to kill random lackeys, episodic bad guys and other unimportant types.
Not that I'm saying this is to the detriment of either show: I love them both.
It's just that sometimes the unkillability of the main characters is a little too obvious.