It's a difficult problem. Survey response scales have probably been a matter of research and discussion before the web even existed.

There are particular instances (like in this case) where there are a lot of incentives for just about everyone to give 5 stars, 10 stars, or a positive and call it a day.

But, in general, there are issues with self-selection, bias toward the high end of the scale, ratings meaning different things for different types and classes of product, etc.