Working at one of the USPS's Priority Mail processing centers, at least one in five packages I see being shipped from one person to another is marked "Fragile". What do people think this is going to accomplish for them?
Let me tell you what a package goes through. The fast version is this: Writing "Fragile" on it gains you nothing. It is up to you to pack that shipment so that the contents arrive intact. The USPS will make sure the package gets there. No more. I highly doubt UPS or FedEx does things any differently.
In an eight-hour shift, I probably handle 10,000 packages all by myself. Dozens of co-workers at this facility do likewise, and hundreds of thousands of USPS workers nationwide move those packages from one place to another.
When a package arrives at the site, it has a lot of company, as it is stored in either large sacks (think of the one Santa carries), or in rolling containers the size of one or two refrigerators. These are dumped onto a conveyor belt, where mail handlers such as myself sort by the first digit of the ZIP Code. This is done by throwing them into bins. Your package flies 15 feet through the air into a box. Twenty to 200 other packages of various sizes and weights land on top of it. These will later be stuffed in sacks according to the three-digit ZIP Code, and then loaded onto outgoing trucks. An alternative to the above involves automated sorting on a machine the size of a football field. Instead of flying through the air, your package goes directly into the sack, moving along a belt at better than a running pace, but also dropping about four feet onto either a concrete floor or someone else's package.
So here's your test for packaging fragility:
1) Place package at the top of a staircase and kick it down the steps.
2) Duct tape together four volumes of an old encyclopedia and drop it on your package, corner first.
3) Have a 50-pound child stand on it.
If your package's contents are properly protected, they will survive this. Myself, I purchase fragile 78 rpm records through the U.S. mail. The shipper regularly ships such records, some of them one-of-a-kind, some of them worth thousands of dollars, using USPS's services. They do all their business this way.
Please learn a lesson from those whose livelihood depends on proper packaging.