I would just like to point out that so far no one has given an actual explanation as to why vampires don't fit the PS settings, other than:
a) they just don't
b) they're from popular culture
c) vampires aren't currently in existence in the PS settings on the website, therefore it is not possible for it to be acceptable.
d) vampires are cliche and they're unoriginal and they ruin all the fun for everyone else in the universe (;P ok, a bit of an exaggeration, but hey!)
Earlier, I posted an explanation of how we could conceptualize of vampires in PS. Not as a race or species, but rather as a disease (which could include both a viral infection or a genetic mutation/disorder). In my explanation, the term "vampire" or "vampirism" is a common term used to describe a being that drinks the blood of another being to survive, thus the word vampire can be used to describe any being on PS that drinks blood.
Siteri pointed out that wereulbernauts were a possibility in PS (as opposed to werewolves, since wolves in fact do not exist in PS), and like vampirism, lycanthropy or were-animal, can be understood as a disease that causes one being to turn into another being for a period of time (such as under stress, during a certain time of year, on command, etc). Would people disagree with an RP where a Ynnwn contracted a disease that periodically turned them into an Enki? Or into a Clacker? In fact, I think I remember a few months ago someone who was RPing that they had been turned into an Ulber... as a curse or something (I can't quite remember). Calling a person with such a disease a were-enki or a were-clacker would make sense, since the prefix "were" is used to refer to their transformed status, not of a description of some fixed being.
So yes, concepts of vampirism and lycanthropy exist outside PS, but they are terms that have been used to loosely describe a general behaviour. The word vampire is only associated to "Buffy" or "Dracula" for some people - usually those whose only encourters with vampires is through these popular culture icons in Western society. However, vampirism has been used to describe many other things: Such as... vampire bats, cannibalism, seductresses, etc.
So this is my invitation for someone to offer a really good reason why people in PS should never try to RP a form of vampirism or other mythical disease, as long as they work it within the boundaries of the PS world.
I think so far the Monstrumis Bloodline guild has done an effective job of this. If anyone can point to something they have done in their RP plot or story line that doesn't fit the settings, I would really like to know.
Karyuu is right, vampirism won't last forever in PS, but it if comes up every so often for players to use to advance their characters and add some drama to the lives of the people of Yliakum, then I don't see why there should be calls for erradicating such RPs as long as they are well thought out. Like I said earlier, I just ignore the RP plots that I am not interested in, and I am fairly certain that most people do as well. If you're tired of hearing about the vampires and you're RPing with a friend who is involved with the RP, just roll your eyes and tell your friend that you're tired of hearing of these vampires and want to talk about something else. People do that all the time in the real world (example: "Ok, enough talking about serial killer X, I'm so tired of hearing about it! Let's talk about something less depressing")