Instead of making people go into Apple Stores, or even worse, submit mail-in rebates, for their free iPhone 4 bumpers or cases (if you don’t know why you’re getting a case, click here), Apple has created an app for the process.
The app tracks your phone by its IMEA, so you can’t get a duplicate case or a second case with someones 3G.
Also, be sure to read the policy on the iTunes page so you get the process done in the correct time frame. Don’t expect to hold off til October and get a case, Apple won’t have it.
It’s a shame that every company isn’t so crafty with its rebates.