Why are Amazon, Facebook and Yahoo copying Microsoft's stack ranking system?
The evil, destructive, part of stack ranking is when you need to apply the 20%/70%/10% breakdowns to all teams equally, meaning that even a team of 5 people needs to have one and only one "exceeds expectation" person and one person who "needs improvement", regardless of overall team level. It's not clear from this writeup that Amazon and Facebook are applying curves at such a micro level.