Apple has decided to give free Bumper or Case to their iPhone 4 users. To receive a free iPhone 4 bumper/case from Apple just follow the guide given below
How to order free iPhone 4 Bumper or Case
Download free app “iPhone Case Program” app form Apple iTunes store.
Run this app in your iPhone 4 and login using your Apple ID or iTunes store account.
Select a Bumper or Case for you iPhone 4. This will ships with in 3-5 weeks.
For iPhone 4 purchases made before July 23, 2010, you must apply no later than August 22, 2010; otherwise, you must apply within 30 days of your iPhone 4 purchase. To qualify for this program, you must purchase your iPhone 4 by September 30, 2010.