Mail carriers will abuse your package more if it's marked as "Fragile"

Popular Mechanics and National Instruments put national mail carriers to the test, concealing accelerometers inside packages to see what pressures the boxes were subjected to. USPS was gentlest, but USPS packages fly express via FedEx, so it's a little inconclusive. This is the finding that I'll remember: "Our package received more abuse when marked Fragile or This Side Up."