What causes damage to hard disk?

[King Belieal]

I have heard of several cases where hard disks get damaged. It can be very fatal to a computer owner when their hard disk gets damaged. What are the things that can cause the hard disk of a computer to get damaged? How can it be prevented?

 

[eLdavis]

In most cases it might be physical trauma from a fall, or liquid could also damage a hard drive as well.