From an *American Heritage* issue some years back on overrated and underrated things:
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Invention
BY EDWARD TENNER [full disclosure: he's my brother--DT]
Most Overrated Invention:
Sliced bread. A late-1920s product that flourished during the Depression and was said to have created twenty-five thousand new jobs, it was technically sound: Moisture circulation in a sliced, sealed loaf is actually improved. But in the long run it helped put family bakeries out of business and promoted balloon bread. And none of several claimants to the invention appears to have made much money from it.
http://www.americanheritage.com/content/invention?nid=59637
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Challenge: During the Depression, family bakeries successfully lobby state legislators and Congress to ban sliced bread. Don't forget that a lot of legislation--e.g., Robinson-Patman--was passed in those days in the name of saving small business from the big, bad chain stores, etc. Furthermore, the technical advantages of sliced bread were not universally appreciated at the time. An article by Bernard De Voto in Harper's Magazine in 1939 stated that "The American housewife hates sliced bread with a heartening violence. She regards it as a scurvy trick of the bakers, a blatant device to make bread grow stale faster. She is right... [De Voto suggests that such housewives either patronize small bakeries or if that is not possible bake bread themselves at home]"
http://harpers.org/archive/1939/07/unrest-in-the-kitchen/ So the passage of such legislation does not seem to me impossible.
Thus, in the US at least it will become impossible to speak of the greatest thing since sliced bread....