As I was saying in the above post, focusing distance plays a meaningful role in attaining that 3D look effect. I'm still taming my new toy, but I feel that 3D cream has a lot to do with blurring the background while having a crisp contrasty foreground.
This is how a 200-meter background would look like at a focusing distance of 30cm
What can you place in front of your camera 30cm away and having a working photo? http://www.box.com/s/aae70139a063c1e4958d
Going back to the very first pic, I think pic number 1 does not work because I'm so close to the excavator itself that it is covering the background, and so there is no contrast between the in-focus areas and the out-of-focus ones.