So many things can go wrong in traditional performance review systems. You can have everything from the manager who is a pleaser and does not want to hurt feelings to some bitter person who blows you up unfairly in a 360. This was a great post by Sean Graber and a killer matrix for evaluation:
Each year, companies are spending nearly three-quarters of a billion dollars in an effort to improve employee engagement — yet you’ll get wildly inconsistent answers if you ask managers what that means. Academics, consultants, and leaders have been grappling with that question for decades.