Car salesmen drive their dealer’s cars. Avon ladies wear their brand's lipstick. Software developers use their own product instead of a possibly superior, competitor’s product. They're all drinking their own champagne. (The metaphor used to be ‘eating their own dog food,’ or ‘dogfooding’). No matter what you call it, it has been proven to work and some companies that you may not have heard of are running away with their successes one great sip at a time.