To Prologue... or Not

Prologue: (from the Merriam-Webster Online Dictionary)

a. The preface or introduction to a literary work.
b. An introductory or preceding event or development.

I love to settle down in my comfy chair, open up a novel, and begin reading a brand new story. I especially love when there is a prologue.

Many readers insist they don't like prologues and even go so far as not to read them. What!? Why would you read a book and not read the beginning? Just because it says the word prologue?
I know several writers who choose not to include them in their work. I have also read published novels that include a prologue when in fact it should say chapter one.

To the best of my knowledge, I don't believe there are any hard fast rules pertaining to the use and construction of a prologue in a fiction novel. They come in every shape and size with an array of content. I have read books where the prologue was a mere two sentences long and others where they stretched into thirty pages. In both cases they worked well.

In a mystery/suspense/thriller novel, a prologue can be used to set up the crime, or tragic life-changing event. Often times the prologue might be in the villain/antagonist's point-of-view. This can enhance the tension when the main characters are introduced. We, the reader, know something our main characters don't. We feel the suspense as they head innocently toward the trap set up by the nasty villain. :)

Perhaps in a family saga novel, a prologue can be used to glimpse a piece of family history. A past event used to set-up the current storyline.

I write romantic suspense novels. In each of my three manuscripts, I begin with a prologue. Each prologue introduces a tragic event that affects the main characters in their present day life. They are life-changing events that help propel the conflict and characters throughout the books.

Over the years I have had each of my three novels critiqued by several different people. Often times it's one of my critique partners, sometimes in a face to face critique group, and occasionally through contests where the prologue/first chapter is judged by an anonymous writer. I usually do quite well in contests, scoring high, but I don't often final, and it seems to be because of my use of prologues.

Is it because other writers don't like prologues? Or they don't get the fact that it's a prologue and not chapter 1? Or am I starting in the wrong place, including too much back story? Probably all of these elements to some degree.
The real questions: How does the prologue enhance the story? Is it well written? Is it really necessary?

Prologues continue to be a great way to introduce conflict, show an historic event, steep the reader in the evil villain's point-of-view, enable us to view our protagonist as a child... or where ever your imagine takes you.

What is your opinion? To prologue... or not?