Ask HN: How to get word of mouth when customers heavily compete with each other?

To clarify: I often heard about building a great product and how that would lead to word-of-mouth advertising from your early customers. But in many cases, I feel customers are competing with each other and don't have any incentives in doing it. Say you are selling something to small restaurant owners and that actually drives sales up. I doubt they will go and tell other restaurant owners about that. And I feel this is actually a very common situation I never hear discussed.