That being said, this is the first one that I’ve read that has slightly touched on one of the major reasons: Mormon nepotism. The Mormon Mafia talk in this article may sound like a joke, but it is very much a real phenomenon. If you hire a single Mormon, and that person achieves a position of influence in your company, you will wake up some day to the realization that there are now hundreds of Mormons...and they all had a say in hiring each other, and they all give glowing reviews about each other, and they all end up in the same organizations, and they all get promoted in lockstep with each other. The Mormon Mafia isn't an FBI thing, it is a real phenomenon that happens in a lot of different places. I got a great job out of college primarily out of Mormon nepotism. I got fired after leaving Mormonism for the same reason.
A good way to prevent this from happening is, not surprisingly, a general anti-nepotism practice: don’t allow people interview candidates from their alma mater. 99% of these asshole Mormons that try to create Mormon Mafias within companies went to BYU, and 99% of the people they want to hire at the exclusion of others also went to BYU. It works surprisingly well for non-Mormon nepotism as well...never underestimate an HBS grad's tendency to think other HBS grads are the bee's knees. Don’t let them have a say in their hiring.