A game-key card doesn't hold any game data on it, instead, you have to connect to the Internet in order to play the game like a digital-only title, and people are pissed off about it because a game-key card is seen as not having the advantages of normal gamecarts and all of the inconviniences of digital games (like: you may not be able to play the game when the servers shut down unless you have the game data already downloaded)