Years ago, a marketing campaign used the phrase "What happens in Vegas, stays in Vegas." When I teach object-oriented design for Java developers and I introduce the concept of encapsulation, I use a slightly modified version of Sin City's slogan. It's meant to emphasize the importance of the Agile principle concerning technical excellence when designing loosely coupled, highly cohesive classes (i.e., designing to interfaces). My version of the slogan goes like this, "What hap