That such a simple word can raise the hackles of so many agents, editors, and writers lends proof to its power. Most people fall into one camp or the other, with the majority, at least those folks who are most vocal, falling into the "prologues must die" camp.
I don't use prologues myself, and I admit that when I see them in a book, I am most likely to ignore them. For me most prologues feel like the author was cheating, as if they doubted their ability to bring a story completely to life, so pulled me aside and said, "Ok, now here's the important stuff you need to know."
While I may not read prologues in my fun reading, I have wadded through my share in a few years of judging writer's contests. While I have never lowered a score because of a prologue, I have also yet to find a book where the prologue was needed.
And right now prologue lovers everywhere are throwing things at the screen :). Let me interject, while I don't feel most prologues help the story, many folks really love them. And the first rule that I think all writers need to stick with (and the only one, aside from "just keep writing, damnit") is be true to yourself. If you love prologues, and feel you have to have them- do it. Just really examine why you are using them. Try taking them out or making them chapter one and see what happens.
To show the other side of the great prologue debate, I wanted to use an example of a successful prologue. I know I've probably got some written examples, but A) can't find them, and B) have found that movie examples often show writing issues better. So my example of a prologue that works is the recent Star Trek movie. The first ten minutes of the film take place prior to the title shot, so I'm calling it a prologue. If you haven't seen the movie, the first ten minutes are an intense action scene in which were are shown that Star Trek cannon will not be followed (aka someone goes back in time and screws things up) and that it's a very rough world we have here. The scene is needed because the actions set up the rest of the movie, ST fans would be confused without it as it changes the life history of the primary characters. Since no one in that first scene is seen later on in the movie (except the bad guys) I think it works nicely as a prologue to give vital information and set the tone for the movie.
Now what about you? Love prologues? Hate them? If you do use them, why?