My elder daughter's boyfriend has taken a big step in their relationship: He's built his own Xbox LIVE profile on my machine. He and my younger son immediately put it to work playing Halo 4 co-op. I spent the rest of the afternoon huddled in my office, trying to work while listening to alternating shouts of frustration and glee (and the occasional cheer-and-confetti from the Grunt Birthday Party skull) filter through my office door.
My experience of playing a game is very different from someone who's playing alone, even if I'm the only one holding a controller. Kibitzing and backseat-driving have been refined and elevated into an art form at my house. Even if there's no co-op designed into the game, it gives us some unexpected benefits. So building a profile on our local device isn't as simple as keeping backup toiletries here. He's joining the team.