Heh, back when Twilight Princess came out, the guy at GameStop was griping that the display cases kept getting stolen... it makes sense now.
Undoubtably the guy selling them either has a connection at GameStop or he's jacking them. (I've gotten about 40 empty DS game cases for my GBA games from my manager friend at a local GameStop. He just gives me the cases from games that people trade in. Most of the time, they have the manual and original cover insert in them. Anyone wanna buy a bunch of DS game manuals/case inserts? ^_^ (they sell the cartridge only as used... that would piss me off, and is a good reason to never buy a used DS game from that particular GameStop. Hell, any game nowadays is completely useless to me without all of the original packaging, blah blah.
I wish Wii game cases were more sturdy... like PS2 cases. Those are quality.
I don't mind Wii Sports being in a non-DVD case. I'm sure there will be other demos and things to follow that will stack up with it.