The main character in the "Mass Effect" series, Commander Shepard, has no arc. He (or she) does not change over the course of the game, does not alter his biases or perceptions, and does not form relationships with the other characters. He doesn't do any of these things because by the very nature of the nano-decisions taking place, he doesn't have to. The character arc in "Mass Effect" takes place in the player, not the character. And that may be the most profound achievement of the series.
At any point the player could switch from answering with nasty and mean dialogue options to being kind and temperate. Or randomly choose between these two styles. There is very little in the game mechanics preventing a schizophrenic approach to the decisions in the game. By virtue of this unshackled process, if a player's Shepard goes from xenophobe to alien comrade, it's because the game changed the way the player wanted to shape his experience. "Mass Effect" forces projection of the player's psyche (or desired psyche) onto a vapid, empty shell of a character. This has enormous impact on the emotional involvement of a player, as the emotions and decisions made by the main character in this epic are by definition the emotions and decisions of the players themselves.
With that in mind, consider the water-cooler conversations around content. For most traditional content, these water-cooler moments (when people get together to discuss the content) represent an exercise in joint attention. We reinforce our communal bonds by reveling in common shared experiences. But what happens when the content is highly personalized? We end up reveling in the differences. On Kotaku, a thread for discussing "Mass Effect 2" players' different endings racked up nearly 700 comments in a day. Offices staffed with gamers have morning rituals dedicated to this sharing.
If we consider that the decisions in "Mass Effect 2" are a reflection of ourselves, it makes sense that we should take such pride and care in sharing them. Much like the "look at me" phenomenon that drives blogging, twitter, and Facebook status updates, when we retell our journey through the game, we're in fact taking an opportunity to show off a part of ourselves.
Both of these forces, from forced projection to an exhibitionistic water-cooler gathering, could be powerful tools for marketers if they were able to harness them. For campaigns that will feature digital narratives, it would be well worth the time to consider the promise of granular "perceived" personalization. There is significant power lying untapped in interactive tales that fail to do so.