The one thing your business needs to grow.
Want to grow your business? Harvard Business Review's Frederick Reichheld says there's one thing that's dramatically more important than anything else: are your customers willing to recommend your product or service to a friend? If they are, he contends, your business will grow. If they aren't, it won't.
Williams Moore's “Brand Autopsy” weblog for that link and commentary on that article.
This rule even applies to Microsoft. Expensive marketing can attempt to overcome this trend, but in this day of word-of-mouth networks that are very strong, if you don't have the best product in a category, word will get out very quickly.