The reason why there are so many rejections is because companies are trying to minimse the false positives instead of minimising the false negatives.
Interviewing is not a standardized test with a standardized evaluation. On the spectrum of human interactions, it's closer to a date, than it's to a test.
In doing interview coaching/training for a living (http://interviewkickstart.com), I see this every day. It's frustrating to a certain degree, but also very powerful once understood.
But hiring somebody bad by mistake, then recognizing that mistake and firing the person? How could that tell this?