As part of the ongoing discussion of Curt Wichter's comments (much of the discussion captured here), I would encourage everyone to read Nicholson Baker's Double Fold: Libraries and the Assault on Paper (New York, N.Y., Random House, 2001). For those doubters that historical materials can be lost even through the best of intentions, it's already happened. It happened seventy years ago.
When microfilm became a new technology (I know-how quaint), libraries had the opportunities to create enormous amounts of space by getting rid of paper newspapers. Those newspapers were laid flat and sewn together one month at a time and took up a great amount of shelf space. Naturally, the thought was and in fact, happened, that newspapers were microfilmed and then discarded. What was lost?
First of all, some newspapers, in whole or in part, were in color. If you didn't know that, then you can see that's part of the problem. Newspapers used to run multiple editions. However, only one edition was ever microfilmed. So, say your ancestor was of meager means and could only afford an obituary to run once. If it ran in the morning edition and it was the evening edition that was microfilmed, you've already lost. And if it's the microfilm from which your digital image is made, you have lost forever.
Most of Baker's book looks at the ramifications from a historian's point of view, but you can see a genealogist being affected as well.