Stickmaster and edge fighter have it exactly right. If you want to get a feel for knife fighting, go ahead and stab yourself a few times. Give yourself a few nice, deep gouges on your face. Because that's exactly what you can expect to happen if you get in a knife fight, or worse. Barring a miracle, you are going to get cut.
How many fist fights have you ever been in where the other guy didn't land a single punch? Even if you totally dominate a fist fight, the other guy almost always get a couple punches in. Envision the last fight you were in, and then imagine the exact same thing happening with blades instead of fists. You got stabbed in the face, didn't you? Maybe the temple? Maybe the stomach?
Knife "fighting" is something to be avoided at all costs. I guess it'd be a good idea to have a grasp of basic technique of you found yourself in a "do or die" situation. However, I kind of think that training for "knife fighting" would serve to reinforce a "stand and fight" response to a situation that would be better handled by getting the hell out of Dodge. Or pulling a pistol.