I'm pointing out that culpability in a perceived bad job performance isn't a two way street and it would be responsible to speak about how you don't always get it right. nothing is more irksome then someone who has fired dozens of people and says they made the right choice every time. statistically impossible.
For whatever reason, only the bottom 5% ever get fired. Where organizations tend to make the mistakes you are talking about is during layoffs, in which quite often, the wrong person is let go - but, in "theory" layoffs aren't performance related - though, in practice, they almost always are. Top Performers are almost never laid off, despite their role in the organization, and bottom performers somehow always turn out to be redundant. One exception to this is when a company drops a division or location - then it's across the board.
Read this: http://bhorowitz.com/2011/08/24/preparing-to-fire-an-executi...