I agree! A Bell Curve is a tool used to manage funds, not develop people.
Unfortunately some organizations still use this process. The advice I give managers who are faced with this tool, is to rate employee performance without the bell curve in mind. Then, once all ratings are complete, compare those results on a bell curve to see if a natural curve exists. In many cases it will. It is easy at that point to stay focused on the employee and not the tool.
Now, when the curve does not align, it is up to the manager to define & justify exceptions to the curve. Most companies should, and will, take these exceptions into account.
The key is to manage and rate employee performance based on employee development...not the curve. This is where a good manager shines.
Hope that helps,
Lisa