The Street (the same people who claimed 1.5 years of free service for the iPhone at launch), now claims that the white iPhone delay is caused by light leaking out the edges, sides and back of the white phone.
Their source says that it's because of the glass that Apple can't easily cover up the light leakage, unlike if it were metal or plastic, where you can just add another coating of material. They also compare it to the Sprint EVO 4G leaking light, meaning that it's not a problem solely in Apple's manufacturing, but it might point again to Apple's pickiness about production quality that they won't let this get out of the door.
So yes, this might be why your white iPhone is delayed. [The Street]