There is another problem with stack ranking -- I saw this at a previous employer: some people are hired into "4s and 5s" from the onset. I heard some hiring managers upset that they would have to force rank their hand-selected elite team into 1-5 ranks, and upset at the situation, they purposefully hired weak workers with the intention of slotting them into 4 and 5 ranks. Their argument was (i dont agree):

- these weak workers wouldnt otherwise have a job

- these weak workers get an extra year of employment they "dont deserve"

- the strong team members get the 1,2,3 ranks they deserve

- the hiring manager is "forced" to do this

All that said, seems incredibly unfair to hire people directly into the chopping block without the expectation set from the start.