If you get the chance to take the side off your camera, you can see exactly what happens. You can do this with power on. Like camergod says, it spools off completely. No danger.
The advantage of a pre-load also comes to play in keeping moisture errors from happening as often.
I also on each load, run bars and tone on the top, do a quick playback for QC. This helps when I open up on a run--roll, I know both tape and camera should be fine at 99.999999%... times. there is always a first for a dead camera. Do remember to power off after you do the above...
Just loading a tape with power down does not let me know if the camera is ready. This QC has saved me more problems than not. A tape that is bad usualy will give up the ghost on load up and a quick roll.
If its bad on spooling, it will lock; if it has dirt, it clogs the heads quickly, giving that dreaded error. If done right, you can check a camera out with time to do repairs , etc...
Since life is about location and timing, every second you save to run-roll will help you get that once in a lifetime money-shot. It happens only once if ever for most.
The danger that I would see is if you have the camera just bouncing about like a yo-yo while you drive, then you face physical damage more than anything else. There a good case, or seatbelted on the front pass seat works.
Now with P2 we get to learn all new tricks... like how to clean balky contacts in the field.
But running bars and tone still has merit, as this way you can do a QC on card seating, etc.
