Anything would be pure speculation, but the hole and dent look consistent with the business end of a forklift / pallet/skid loader.
And we got another one damaged in the same way a day later. That one just had a hole into the top area though and got the mouse only. But both of them went back.
I work for the Department of Redundancy Department
I talked with the fedex guy and he was floored to see it. He says that shipments of this type are not normally handled by forklift. Larger computer boxes of this type are moved by hand. Carried, or placed on a two wheel cart. (and I'd imagine the new weird-angled imac boxes are causing enough headaches too)
So he was actually wondering if it came from Apple that way. But they'd have to be pretty negligent to accept a box with a hole like that in it for shipping.
I work for the Department of Redundancy Department