Just to address alc's point about people not reading the prologue, and connect in to Toby's about epicness -- I will normally read the prologue, but:
- I will hate you if you kill the POV character at the end of it because, as others have said, I resent getting attached to someone and then having them killed off. You will have to work hard to get me interested in the next POV character because I suspect you of intending to kill them off as well.
- Connected to this -- and this is completely personal preference -- the sort of writers who introduce people just to kill them tend to be making a point about the gruesomeness of life in whatever period, and their story tends to be far bigger than any one person (e.g. "A tale of the politics and intrigues of several generations", not, "A story about Fred the pot boy who discovers a magic sword and...". While I've had enough of Fred and his relatives, I far prefer stories where the author starts with the person we're interested in.
- If the prologue's about gods or myths, I will give it about three sentences to interest me and then I will skim through it. If it's longer than a page, I'll skip it.