For current iPhone 4 users who want a new Bumper or other case, you’ll have to download the iPhone 4 Case Program app from the App Store. When the app launches, you sign in with your Apple ID, and you’ll be presented with a selection of cases to choose from. Currently you can choose either a black Bumper or one of seven cases from InCase, Belkin, Griffin, and Speck.
Doing it through an app is a clever idea. Also interesting: only the black bumper is available through this program.