Many moons ago, while back packing, I sent a parcel home from Australia to lighten the load.
For customs you were supposed to declare the contents, so I reluctantly wrote "Sennheiser headphones" amongst other items.
When I got home and looked at the parcel, it was obvious that it had been opened. The headphones, (a high quality pair), were gone. The china and porcelain items brought back as presents and carefully wrapped by me had all been undone and just chucked back in - luckily none broke - and bizarrely, there was a T shirt and pair of shorts that were not mine but resembled ones I had put in.
Obviously, somebody in customs has all the parcels opened and anything of value is nicked, and then the contents just shoved back and very badly resealed and posted on. In my case the wrong, but similar, contents !
Never let anything of value out of your sight.
Also, assume that any bag put in the hold might be dropped from 6' onto concrete. This is not necessarily deliberate, but bags do fall from the aircraft holds or baggage trucks when loading or unloading. I occasionally have to ask the loaders to be more careful, and was physically assualted by one charmless **** at Luton, when I took exception to him just throwing the customer's cases at the loading belt and dropping most of them onto the apron from height.