Iwata: DSi XL is a spectator system
He envisions the DSi XL as allowing for a "new play style where those who are surrounding the game player can also join in one way or the other to the game play." Tomodachi Collection, one of the best-selling DS games of the quarter in Japan, is named specifically as a game that already benefits from having friends nearby. "Because communications and interactions with other family members and your friends are one of the key elements of the game, the fun aspect is intensified when other people can watch how you play in comparison with when you are playing by yourself."
As a bonus, your friends can help you hold the system up.