The aim of brand builders is to engage with consumers to the point where they become apostles for the brand, an much effort has gone into developing measures that use this notion as a measure of brand strength.
On the other side of the coin are the detractors of your brand, and the damage they can do.
The development of a brand therefore also has the two dimensions. Powerful brands encourage powerful emotions, and some of those are very likely to be negative, it almost goes with the territory, anything capable of arousing powerful positive emotions is just as capable of arousing negative ones. An overlooked, but key challenge is how you manage the detractors, and the things they use as hooks for adverse comment.
Recently a measure “net promoter score” has become the favorite or marketers, as it appears to offer a methodology of collecting quantitative data on the behavior of your customers. Introduced in a 2003 HBR article by Fred Reicheld it has quickly become accepted as almost gospel.
However, experience suggests we should be pretty careful when someone has all the answers to all our previously intractable questions, and it is no different here. NPS is a great start to measure those who use, or have used your product, but relying on it solely to save the day is a big ask.