It would have the same effect that culling the bottom 10% would have. You promote mediocrity. Think of it like this: employees game the system by avoiding the "fireable" qualities and rush to the "hireable" qualities.

So everyone in the org wants to appear like a young firebrand and hide in the school of fish. As outliers are singled out, those who blend in well and play politically with their managers have the highest survival rate despite not being the most productive, as they devote most of their energy to not standing out.

In any persistent environment when you add pressure, you develop a counter-reaction. You can't change human behavior with simple levers, but you can bring out very human behavior by doing so.