'Lost BBC Programmes' is a common topic.
"2" VT's re-used due to cost".
"What a waste of old material".
"Missing Episodes of Dr. Who".
Here is an article describing the costs involved by the movie business.
Meanwhile The British Library has launched a project to rescue 500,000 recordings, threatened by degradation, or the demise of the original recording medium. "Unlocking Our Sound Heritage" will, they claim, save music, pirate radio, spoken word and field recording. More information is
here.
Sources:-
"The Institute of Electrical and Electronics Engineers" "Spectrum".
"The Vinyl Factory".