Well, it looks like you can put those conspiracy theories to rest... or can you? Apple has just put out an official statement on the nowhere to be found white iPhone 4, which it now says will not be available until the "second half of July." What's the holdup? Apparently, the white models have "proven more challenging to manufacture than expected" -- but don't worry, Apple assures us that "availability of the more popular iPhone 4 black models is not affected." Complete statement (which you've mostly just read) is as follows:
Statement by Apple on White iPhone 4

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.