p.s. 

here's a few items I can attest to that are relevant, I believe;

Way back in the '80's an editorial appeared in the op-ed section of the local paper bemoaning the fact that, for the very first time, a portion of a US census had become inaccessible. 

It seemed that the 1960 census was the first one that was NOT fully printed out to hardcopy. A lot of the data was stored on magtape that required special 'readers' to access the data.

The special reading device had long since gone out of production & the last one had just broken down & was unrepairable.

He then went on the speculate about all the data that was currently stored exclusively on magnetic media.

At the small college where I worked for 30 years something similar happened.

A whole bunch of financial data was placed beyond reach after various equipment upgrades over the years rendered the data unrecoverable.

I was actually put in charge of trying to recover & convert as much as possible but by the time I was assigned the task a great amount of data was already lost.

I suppose, in theory, all the data in both examples above where theoretically recoverable but there's always the issue of cost, don'tcha' know.

In the second case, during a major remodeling, all the old unusable media was discarded.

I was in charge of that too. I worked graveyard, so, every morn, just before the garbage trucks came to empty the dumpsters, I hauled a load of boxes, full of media, out & dumped them in.

But even that wasn't enough so when we ran out of time my boss noticed that there was an unlocked storage room inside a building that was due to be gutted so he stuffed it with what was left over & locked the door behind him! We never did hear what happened to those items.

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