John,
I really appreciate your comments on this thread, they are thought provoking. A few thoughts I had:
1) How is walkability defined? A course that most could walk, or in the negative, one that most would choose not to play if a cart weren't available. I'm guessing most golfers would find a course like Augusta National a difficult walk (and assuming it were not ANGC and they could regularly access it), I suspect most would take a cart when they played it.
2) A course like Sanctuary I would certainly deem unwalkable, but in my one playing I found the course very interesting and fun to play, even if the difficulty of the terrain basically demanded the holes be built far apart with lots of up and down. There is a similar course here in SLC with lots of neat and terrific shots, but also basically unwalkable.
3) And then there are courses built in very hot climates where walking would be borderline dangerous, even if it were dead flat.
P.S. On a side note, I'd be interested in the thoughts from those who have played, Lawsonia, Mammoth, and Landmand as Jason asked a few posts ago. How do those compare relatively speaking in the big and bold category? To me, (based on pictures and flyovers), Landman looks very compelling.