Is Customer Feedback Survey Useless?

Is customer feedback survey useless? Has it lost its original intention?

A "Customer Feedback Survey" is often used when a project completes or a master contract expires. Customers are to fill in a customer feedback survey form to indicate how satisfied are they on a project outcome. A rating scale is usually used, for example, rating of 1 indicates "Poor" and a 5 indicates "Excellent".

This system may seem to be quite effective, however, there lies a very serious defect. Problem arises when customers start giving majority rating of 5 for good which is lower than excellent. This realistically exists when the relationship between the customer and the provider is good. Another different customer may give a rating of 4.5 to reflect excellent. See the catch? I personally feel a score of 4.5 out of 5 is already in the excellent band, however, he may end up in a lower band due to another customer giving 5 for a mere "Good". In real world, the guy giving a rating of 4.5 may end up getting a "scolding". Who knows all will give 5 the next time!

Back to my questions on the effectiveness of "Customer Feedback Survey", I have actually given my answers above.