The worst "nuke the file system" experience I had was on the GE mainframe.  Think big room, punched cards, etc.  And an operators' console that typed on paper...

When you booted the system, the first message that came up said:

    INIT?

If you said 'y', it wiped out the file system.

After a very heated users' group meeting, they agreed to change the message to

DO YOU WANT TO WIPE OUT THE FILE SYSTEM?