There have been reports from users that cracks are visible on the iPhone 3G, more so on the white iPhones.

The high visibilty on the white models could be due to the dark hairline crack on the the white surface.

Owen Cropper says:

I have exactly the same defect – small hairline fractures in corner, did not notice when picked up but absolutely have not dropped or banged- I am on hold to ask for a replacement. It is a manufacturing defect that I suppose is a stress fracture or something. I will let you know if I am successful I will post all over god’s green earth on the blogs if they do make good – I suspect they will.

The issue seems to be only cosmetic and it doesn’t affect the functioning of the device.

It’s plausible that it’s only the paint that has chipped off since plastic wouldn’t crack easily.

A wide array of solutions have been offered by users such as applying Brasso to using Power Support Crystal Film.