I just called Otterbox to help a customer with an issue with their iPhone 3G case and holsters. The problem is the "Air bubble" or "Spilled oil look""
I am going to give you a few different solutions and one of them is different, but has been known to work.
Take the phone out of the case. You will want your hands to be clean, but not just washed. You want to take the palm of your hand and press it lightly on the front panel of the otterbox (the part that would touch the phone). It seems like there might be finger prints that would show on the screen of your phone, but they do not. The natural oils of your skin should help with the oil/bubble look on your screen. 2. To remove the "oil spill" look on your iPhone 3G's screen, follow these simple directions:
1) Fill a glass with about 10oz of water.
2) Put ONE DROP of dish soap into the water and stir.
3) Dip the tip of your finger into the water solution and then rub just a LITTLE on the screen of your device. Remove any excess water.
4) Place your OtterBox onto the device and smooth out the bubbles by GENTLY rubbing a credit card over the top of the screen.
If you follow these directions, you should completely get rid of the "oil spill". Some people have said that simply rubbing your finger on the inside of the screen membrane works as well. Doing this and then smoothing out the screen with a credit card is another option.
It worked for me and my customer. I'll also post this in the iPhone section.