This is a very interesting topic & something that I've wondered about many times when you send something valuable into the hands of the others hoping it will arrive safe & sound. I've also had a bad experience with the USPS regarding getting them to pay what the item was insured for. Similar to what Ron states about FedEx, the USPS will happily take your money but will buck when asked to ante up on an antique item that goes missing, particularly if the item is a 3R militaria item.
I had a lot of trouble even getting my out of pocket cost for the item back from them. Forget about the fact I paid several hundred dollars less than I could have sold it for, I still conisdered it a moral victory I got something back.
I think many of us luss ourselves into a false send of security that a shipped item is "insured", but we really need to anticipate how a carrier will react in the inevitability they lose something of ours that's valuable. I guess a good suggestion is if you have to ship something valuable that you first get some sort of valuation statement from some sort of "expert". Despite my small experience I would still say I'm more comfortable with the USPS than the other two major carriers.
