I can’t tell you how many times over a multitude of  years witnessing a student panic due to fears of wiping out a file! It is frustrating putting a lot of time and effort into one’s work only to have it disappear in a matter of seconds!!! This is no longer an issue thanks to Google APPS for Education when creating a doc, presentation, sheet or drawing!  Thanks to the Revision History one can restore their work from a previous revision completed before the delete key was clicked.