rugged - cardboard + latex is a good idea (have a look at the pencil pouch)
compact - in a shape of the camera, foldable (flat) so that we can save some space while the case is empty
perhaps even waterproof
Thinking about the shape - I really like the idea of the orishiki suitcase. It is sleek, stiff and can be stored flat.
The camera case could be made using the same principle.
Here is a really nice kinetic sculpture by studio lab[au]. It reminds me of some sort of membrane hinge surface. i think it is a good concept for creating the shape of my camera case.
I also had this mad idea of creating a camera cage. It would provide maximum possible protection for the camera. Perhaps it could be an addition to the camera case. The case provides protection from dust, dirt and water and the camera cage protects it from everything else - being squashed, stood on, dropped etc. I imagine it would be a part of travellers kit, perhaps the camera could even be used while staying in the cage.
Here are some pictures of a prototype I've made: