Vampires and zombies

Vampires are huge right now, as are zombies (though zombies aren't quite as huge). What's the ground of their success? Well in their current, Twilight-y/True-Bloodish iteration, fairly obviously, vampires mediate sex via death. That there is such a huge cultural appetite for this morbid erotics is interesting in its own right, but I'm more concerned at the moment with what it is that zombies mediate via death -- since, like vampires, its their thanaticism that evidently grounds their appeal. What do zombies mediate via death? What else but death itself? -- the short-circuit of non-existence not existing, 'being' itself burnt out and blasted? Vampires are the dead who are really alive. Zombies are the dead who can nevertheless die, the tropes of an uncanny reduplication of death: an unsettling potlatch of death exchanged for death.