These five people you mention did not fail the "test". No one has ever passed or failed the MMPI.
It really shouldn't be referred to as a test. It is not a test, but that is the common vernacular, it is an
inventory of personality traits. The test results had nothing to do with your friends not getting hired. The MMPI doesn't determine these things, the employer does. The employer establishes the hiring criterion and the MMPI revealed to the employer that these individuals did not have the personality traits the employer was seeking or did have traits they were looking to avoid. The employer might have been looking for specific sets or combinations of traits and your friends simply didn't possess them. It's hard to say without detail. The MMPI is not an "intelligence test". It doesn't care what you've achieved in the past, what accreditations you've earned, or whose recommendations you've accumulated in a given field. If as you say, you were the decisionmaker or authority in hiring these people, you should have known how this inventory works and what traits were desirable or not. In most case the results are kept very confidential and are only viewed by those above certain confidenatility levels with HR departments. I have to say, while reading your post I couldn't help but think you may not understand its purpose. I'm certain each of the inventories revealed differing traits for each person and If your saying you are a better judge of personality traits...that's fine. That's an opinion you're entitled to, but it is completely contrary to a much greater knowledge base and the resultant opinions of a whole lot more people who I'm certain know a great deal more about the subject than yourself.
I understand you're only expressing your opinion based on a coincdence. But, I think we need to avoid vane attempts to discredit things we know little about.
More on the MMPI and it's use in hiring:
http://en.wikipedia.org/wiki/Minnesota_Multiphasic_Personality_Inventory
http://en.wikipedia.org/wiki/Employment_testing#Personality_tests