.................
Probably more important than excessive padding is making sure the item can NOT move any way inside the packaging. If it can move, it can beat itself to death!
I'd agree, but if what you use doesn't fit the guidelines, the shippers will take you to task for it (i.e., say it was packaged improperly).
I suppose there could be an argument for packaging that is too rigid just transferring shock to the item wrapped inside, but I am not a dynamics engineer doing shock analyses. 
I remember years ago shipping some Acela cars to Lionel for exchange and the guy at the UPS store asked how I packed them (probably due to the amount I insured them for).
When I told him I had padded everything very well with crumpled newspaper (rigidly, not just a few loose pieces), he told me I improperly packed it (newspaper is apparently not approved for insurance claims) and should have used packing peanuts (which they just so happen to be selling bags of at the store).
There is no way I was about to unpack what I had done and "half fast" (apologies to Verizon) it with a quick repack in the store.
I then told him since it was an exchange I was primarily insuring it just in case they lost my package, so if I had to make a claim, no one would ever be able to prove I didn't pack it right. I'm not sure he liked that part of the conversation. 
-Dave
