The office I work in has lots of hard-walled offices with doors around the perimeter, and open space in the middle that is filled cubicles. The cubicles are surprisingly nice-- they're Herman Miller with high outside walls, sliding whiteboards, sliding windows between cubes, and organizing shelves. Most importantly, they have full-height doors that slide closed.
The people in offices almost always leave their doors open unless there's a meeting going on.
The cubicle dwellers almost always close their doors whenever they're at their desks.