Heh.. It seems that in the US, the Kodak Canon mount DCS is going for like US$2.5k new.. Apparently due to some dispute as Nikon didn't like Kodak hacking their bodies (Kodak only manufactures the sensor and the firmware, the rest of the entire body & electronics is built by Nikon) into Canon mount.. LOL..
4/3 is not a sensor ... its a lens mount ... but cameras that the 4/3 lens mount are the oly E1 and E-300 ... they use full-frame ccd sensor with 2x crop. if u're gonna quote me on fullframe being 35mm ... thus should not have any crop ... go do some reading up.
Nope, the focal length is still 18mm when the marking on the lens barrel points at 18mm. But because of the crop factor, the field of view of your D70 at 18mm is equivalent to the field of view at 27mm of a normal film (35mm) frame (i.e. narrower).
The crop factor changes the field of view, not the focal length per se.
Crop factor is more for the knowledge of those who are used to the 35mm film frame size. For newbies in photography, it shouldn't matter so much, if at all.