No one should despair as there are many other factors that come into play with an MBA application - your professional experience actually being the most important. For example, I was working with a mid-level manager from a pretty big finance firm who wanted to get his EMBA so he would have some solid credentials, but he couldn't break a 580. He still got into Yale.
That said, I believe people do need to be realistic about what schools they're targeting and if they're competitive. I often have clients call me up and tell me they want to go to Harvard or Wharton and their score (and experience, or years out of school) just isn't going to get them there.
So, it's not completely black and white, but that doesn't mean that if your scores are truly horrible that you should think HBS is a real possibility. Look at yourself realistically, take some chances in terms of long-shots because sometimes you're never going to be happy unless you try, but cover your back too, by targeting some mid-level schools. Admissions is subjective: a lot of different things come into play and it's all about your overall package.
Jillian, President & Founder
MBA Ivy League
New York, NY
https://www.MBAIvyLeague.com