The App Sandbox is a great end-user security concept. The Sandbox governs what an application can and cannot do. This means that a virally-infected word processor, for instance, cannot go and infect other applications or rampantly damage files on the user's disk.The developer's pain comes from the App Sandbox's greatest strength. The app developer must perform additional work just to reclaim functionality that the App Sandbox took away! But if you want to sell an app in the Mac App Store, the app must adopt App Sandbox security.