Cracks 'appearing' in new iPhone 3Gs - The Unofficial Apple Weblog (TUAW)As an Apple customer, I'm used to this. My MacBook plastic cracked, my iMac display partially delaminated, etc.
...The problem is not the plastic, but that the metal frame is too small for the plastic to lock on without causing the stress fractures.' It's pretty clear Apple has a manufacturing defect on its hands.
For those with cracks, taking it back to the Apple Store (or possibly the mobile phone retailer where you made your original purchase) is your only recourse. Several people have noted here and elsewhere that they've successfully had their handset replaced after a careful inspection....
I have a 3G iPhone so I'll watch for the cracks. Might be important to get their existence documented early to be in line for a recall solution.
I'm not sure what the value of a phone swap is, if it's a real manufacturing defect the new one will have the same problem.