Had mine for 2 years and it's picked up the odd dust spot. I just use a blower and, like others, always hold the camera facing down when I change lenses and try to be as quick as possible(without dropping it!).
'Spots' when they occur always seem to show up on areas in the sky and I find them easy to remove on the computer(I use Aperture)
I just wonder if the OP was shooting in a particularly dusty environment? My earlier camera was a D5000 and I used that on safari in Tanzania without any serious problems(and it can get very dusty there. I was changing lenses in the back of a Land Rover too-not an ideal place!
It does seem that some bodies(and users) suffer more than others and there seem to be 2 issues - one oil from the body itself(send it back for Nikon to fix) and dust incursion