"A better use for transmedia is in an area that games are the worst at: propagating backstory and exposition. Portal gave you context brilliantly in-game with environmental storytelling - posters, bloody handprints, abandoned coffee mugs. But in general, the narrative of a game is told much less subtly than that. We have libraries full of history books, awkward NPC monologues, and the same information duplicated by every other NPC. The quest formula and cut scenes. These tools are often used to carry the entire payload of story in a game, and they create a serious friction problem."
Absolutely correct--and it leads me to another leap in insight, which is that films are nearly as awkward a fit for backstory as games. Screenwriting emphasizes forward motion of the plot--rightfully so. Films with too much exposition are difficult to sit through.
Good insights in this article.