"Your most loyal customers set the stage for continuous volume growth. If you listen to them, they can help you define how far afield you can extend. If you track them and induce them to introduce you to their friends and family, they can be your surest route to growth. If you forsake them at any point, they can, like jilted lovers, go from being fanatical fans to fanatical detractors. They will tell you in clear language what is a sin and what is unacceptable behavior. But don't turn away. You need to listen, question, listen again, and test."