I've been reading NewEgg's reviews, and I'm wondering the same thing about hard drives as this thread does about mainboards --can there really be that many DOA ones? I mean, it is easier for poor shipping to cause failure, but it's hard to believe the number of complaints I see on WD and Seagate drives. Some people have blamed that on manufacturing quality changes when moving production to Thailand, but not being a production engineer, I have no idea, and I'd be prone to doubting it.
For hard drives, poor shipping used to really do a number on them but recent drives are made a lot better now. When they are powered down, they can take a lot of g-forece and vibration and still function properly. Newegg tends to package bare drives wrapped in a thick layer of bubble wrap and or plastic case with spacers and cushions, so the likelihood of the drive experiencing close to 300G's is low unless the shipper does a rugby kick to get your drive to the door from the street. When the drive is operating, the drive can only handle less than 1/10th the G's before the drive is damaged. So the tower falling over on a hard surface, dropping the tower while it's running, etc etc can damage it pretty badly.
One of the biggest culprit I suspect is static. Mechanical failure takes a while for it to happen, and even after a bad drop, the drive usually still functions but with bad sectors. If the circuit board dies, it dies instantly, and many drives have exposed circuit boards that can die instantly due to shock.
Even after grounding my self, I still try to avoid even coming close to touching the circuit board... but I've seen a lot of people that "man-handle" the drive and smear their greasy hands on the circuit board while installing the drive. I think a lot of people underestimate the damage static can do to electrical devices. I've even seen "professional" system builders do the same thing and leave greasy fingerprints on the chips, and various components inside the computer. There are ways to design a circuit board to be resistant to static damage, but internal computer parts aren't designed that way, because static isn't a threat once it's built. Many high quality cellphone boards are static resistant. I zapped a old LG Env main board with a tesla coil for about 20 mintes, and surprisingly, everything still worked.
I've also seen some people try to install the hard drive while the system is on and kill the drive. Other times the PSU was bad and over volted the hard drive and killed it with a small puff of smoke