This is from Stephen King’s “Everything You Need to Know About Writing Successfully – in Ten Minutes”.
It's an article believed to be from 1986, and it's about how to write. Number nine reminded me a lot of customer feedback, and I think King sums it up well.
9. How to evaluate criticism
Show your piece to a number of people – ten, let us say. Listen carefully to what they tell you. Smile and nod a lot. Then review what was said very carefully. If your critics are all telling you the same thing about some facet of your story – a plot twist that doesn’t work, a character who rings false, stilted narrative, or half a dozen other possibles – change that facet. It doesn’t matter if you really liked that twist of that character; if a lot of people are telling you something is wrong with your piece, it is. If seven or eight of them are hitting on that same thing, I’d still suggest changing it. But if everyone – or even most everyone – is criticizing something different, you can safely disregard what all of them say.
Basically, the customer is only right when it's a group of customers.