Large scale ARG (Alternate Reality Games) like the one above would seem to me to be forever capped by the number of people that can effectively take part.
You have to go to certain locations, in the real world, at certain times. This ethos is completely different to every other new form of distribution. The general trend there is much more in the direction of 'watch any story, whenever you want, wherever you are'.
That must be a big part of the appeal of the ARG of course. That it flies in the face of the trend. It is a live gig rather than mp3 download - if you follow the analogy. But it probably goes beyond that, it is more like following a whole tour, rather than going to one gig.
The time isn't so much the issue. I'm 80 hours into playing the PS3 game Final Fantasy XIII. And lots of people happily watch 24 episodes in a box set. However, these fit around other commitments and activities. We chip away at those big stories. The specific time frame that is enforced in an ARG must surely limit the people who can enjoy it.
What would a time-shiftable, real world, ARG look like? Is it feasible?
I found out about this via the Transmedia Storyteller forum - check it out if this kind of thing interests you.