Employee performance reviews that enforce an arbitrary curve-based ranking or grading system often to do more harm than good.

I have seen employees who have performed well all year get demolished by a performance review where they were rated a "3" or "4" out of "5" because HR required only one "5" per department and two or three "4"s, and expect the majority of employees to be a "3". (Thankfully, they didn't require that each department designate a "1" goat.)

That being said, I have found that performance reviews that focus on how the employee has improved the business and seized opportunities (or not) and focus less on artificial competition are extremely beneficial.