Great subject Dave.
I understand what your saying but I do not agree the amount of carnage possible is the the correct method of determining what is or is not subject to physical damage.
IMO subject to physical is all about the location.
Take a look at this 4" RMC that had a service conductor fault.
For more.. http://electrical-contractor.net/ubb/Forum5/HTML/000801.html
My point here is that faults can and often do happen in metal raceways. When service conductors are involved RMC does not help much to contain the sparks.
I have lived all my life in an area that uses SE extensively, I can tell you these services are not blowing up, burning down etc.
I installed an SE service on my own house after bending up some RMC and finding it too ugly. (The Meter is tucked into a tight location)
IMO some sort of current limiters at the service point would be a good idea but I do not see that happening.