From the Zappos Experience by  Joseph A. Michelli:

In order to get customers to refer you to their friends, you need to have employees who are deeply loyal and who themselves are evangelists for your brand.  

He also mentions a blog called Church of the Customer, where Ben McConnell wrote:

Companies with great word of mouth tend to operate by a simple, yet inspiring purpose and well-defined values.  They have created a culture constitution, and every employee is sworn to abide by it, so help them God and the HR department. They understand that a purpose-driven company helps clarify decision-making while inspiring longer-term unity."  

Agree wholeheartedly. With purpose you make decisions from an entirely new and different perspective that feels just right.