There are several reasons to back up files.  Each demands a different approach.

1) Protect against file deletion.

You will delete files.  Someone else will delete a file that is important to you.  Your IT guy might empty your trash absent-mindedly while fixing your printing issue.  Your cat might jump onto your keyboard and “accidentally” hold shift and delete at the same time.  I think we can all agree that at some point files will be deleted.

2) Preserve versions of files.

Sometimes you accidentally save over a file.  Sometimes, you do a lot of work and think it looks great and purposely save the file, then you show it to your collegue who you are in love with who will never notice the way you dreamily gaze at his/her exquisite smile, and that person suggests it looked better yesterday…hope you have a backup. 

3) Loss or Theft

At some point, sleep deprivation catches up to even the most seasoned traveler, and a laptop is left behind on a plane, or in a cab, or at a massage parlor.  You may have parked the rental car in a public lot to stop and check out the surf, but the guy who waited until you walked away and popped your window just scored a lightly used MacBook Air.

4) Hardware failure

The tape companies love telling you that it isn’t a matter of if your hard drive will fail, it is a question of when.  And, assuming you use your computer long enough, they are right.  Tapes fail, too, btw. Every component in your machine can fail, and some of them take out others.  Sometimes you were hitting on a hot doctor from cardio and thrilled about the super clever jokes you were firing earlier over coffee, and you turn on your computer to post a Facebook status update, but nothing happens, and you realize that the hug you were about to virtually hgih-five yourself about meant that your laptop spent 30 seconds pressed up against the artificial-heart-stopping magnet in her labcoat pocket.  Shoot.

5) Catastrophe

Natural or man-made, disasters destroy computers.  Floods, fires, and wolverine attacks all destroy computers. 

I am willing to bet that 2 (or more) of these 5 have happened to everyone reading this. Can you think of other reasons to backup files?  Can you think of a reason not to?