I can easily imagine the guy taking all the pictures of the unboxing. I did the exact same thing when I got my 400 f/2.8, and something similar when I got my iPF8100.
It's pretty clear that there's some sort of fraud going on. While it's possible it's the irate customer is the one committing the fraud, I have no trouble believing that the distribution center got compromised, that several boxes had cameras replaced with flooring, and they do so little business that the replacement was sent from the same compromised batch (or that an employee was doing the replacement on the fly, and the same one handled both orders). One would think that Dell would have ordered an immediate inspection of the inventory, including sampling of that particular lot, but it's not at all hard to imagine the sort of corporate incompetence that would result in that not happening. Especially if order fulfillment was (as Dell admitted) outsourced to the lowest bidder.
I trust B&H, and they'll continue to get my business. Dell...well, everything about Dell that I've ever dealt with has been about nothing but the lowest bidder and driving down prices. I value my money too much to waste it by being cheap.