Thank you all for your comments, you guys are right on. Jeramiah brings up a good point, that is the importance of "stiffness" in the transmission of force from one link to another. Porterfield, McGill & Sahrmann always allude to the importance of this in the prevention/rehab of back pain. In this vein, Vern always mentions the importance of throwing med balls, but also catching them. It's important to remember that one segment is slowing down as another is speeding up, and that requires proper stiffness about a joint(s). Vern also makes the statement that no more than 15% of your core training should be on the floor, and I think that is accurate and is consistent with the Japanese research. I agree with the group, that even if the rotation is taking place air born like a volleyball strike or a dive, the momentum is still initiated off the ground.
Many of the injuries attributed to rotation (disk injury, pars fx, et al) have a multifactoral etiology beyond the scope of this blog. It doesn't change the formula for a healthy back: Push, pull, squat, rotate, reach in a sound progression.