There really is no way for them to stop people from doing this.
Sure you can not do an exact exchange, but they can not stop you from returning the phone within 14 days, resetting your contract, and then going back in to buy a white iphone when it comes out. YOu may have to wait a week or so, but by that time everyone who bought a black one will have scratched their iPhone 4 itch.
Oh and the restocking fee at apple stores applies to non defective items. If you push the issue, I know you could get the fee waived due to the reception issue![]()
I'd have no problem with it if the black iPhone owners had to wait a week. It's the whole launch of the white iphone i'd be pissed about.
If you returned the iPhone because it was defective they'd give you a black one. Just like when you take your iPhone into AppleCare, they replace like for like. No black-white trading. So it goes back to trade black for white and pay $40(?) and wait a week or stick with the one you bought.