That last happened to me fairly recently, when a server was unable to mount /usr (where the termcap stuff lives) and I had to use ed to edit the RAID config files so that I could mount it. Fun times.
Ouch, more extreme than I was thinking. I've encountered systems that don't like screen or urxvt or what have you, but they still had vt100 and that's a useful subset of the termcap of most modern terminal emulators. If there's no /usr at all, that's certainly a stronger argument for ed!
