My prologue is a scene where my MC is getting beaten up by her boyfriend and this is what causes her flight across the country. Without it, it just doesn't make a lot of sense. And the scene is pretty grabbing. The first chapter starts with her running out of money and gas...which would be kind of a boring place to start.
The problem with starting like this in a prologue -- and everyone knows that I'm anti-prologue, so take my comments with a bunch of salt, but please do consider them -- is that, in general, we don't care much about a person who's being hurt unless we already know the person. That sounds callous, and it's a bit of an exaggeration, but it's human nature. If our sister (or brother, mother, child, etc.) is being hurt, we're much more likely to go ballistic than if, say, someone on the other side of the world is being hit or even a stranger is being hit. So, starting with a character being pummeled is actually less emotional than you might think, if we don't already care about the character.
Now, consider the running out of gas scenario. We've got a character, and she seems interesting in the first sentence (that's the hard part of charcterization, to make the character real and interesting quickly, so I'll leave that up to you), so we read the next sentence, and we realize she's got a problem (running out of gas), and she's doing something about it presumably (we like people who are pro-active, rather than passive), and we can start to settle into her skin, decide that she'd be fun to hang out with for a while, see if she can resolve her problem (getting gas). And there are hints being dropped that she's running away from a serious situation (the beating), perhaps she covers up the bruise on her wrist so people won't see it or whatever, so the reader knows that there's a bigger problem (the beating and the boyfriend) lurking in the background, so the reader turns the page to find out what that bigger problem is, and how the character is going to solve it. I don't need to see the beating to understand it, and the real story is in how the protagonist copes with the fall-out from the beating.
Dole out the important stuff (from the past) in dribs and drabs, showing the protagonist coping with it, and it's often actually more effective, more emotional, than dumping it all on the first page, where you've given away all the suspense/mystery about the character, which removes some of the impetus to continue reading.
Often, writers need to write the prologue to fully understand the backstory -- we're writers, after all, and we wrap our minds around stuff by writing about it -- but the reader doesn't need to know that until it's relevant to the current story.
JD