Well, in a recent presser on top of the Droid X event, Apple has the following to say about the white iPhone 4 magical delay:
CUPERTINO, Calif., June 23 /PRNewswire-FirstCall/ — White models of Apple’s new iPhone® 4 have proven more challenging to manufacture than expected, and as a result they will not be available until the second half of July. The availability of the more popular iPhone 4 black models is not affected
It’s probably due to one of the following things. Either the new iPhone 4 in full white casing is harder to produce than expected, or they can’t find enough unicorn fur to build them. I’m going for the latter. Possibly.