I don´t think that it should be explained in details why world of mouth is important in customer experience management.
Have look at this great infographic done by WOMMA about world of mouth.
From toothpaste to travel, there’s one thing that influences decisions more than any other source: word of mouth. We like to talk. And while we talk a lot about the usual stuff, our friends, family and careers, we talk surprising amount about products (and services) and not just about the latest iPhone or how you can return anything at Nordstrom. How much? We’re glad you asked.