Because D700 is a high volume camera, the D3 is not. We will though consider pulling out the D3 into its own forum now when another "invariant" of the D3 is about to come (according to rumors of course)
Visit us at Photokina, Cologne Germany, September 23rd-28th 2008 We're in Hall 2.1, Booth E014
To my mind the D700 is effectively a D3 with the bulky bottom chopped off. I know there are minor differences like fps and shutter life but the sensor, most of the gubbins inside and the image quality are identical.
However, because it lacks a bulky bottom, it seems doomed to be labelled 'semi-pro' despite offering the same imaging performance.
At £2,000 body-only it's hardly a high-volume camera, more a back up for professionals with D3s, or in my case the main camera because I don't want the bulk and weight of a D3 round my neck for hours at a time.