Or more to the point early versions of the MS Office suite, where major updates could and did create backwards-incompatible saves. Users had to be careful that

Or more to the point early versions of the MS Office suite, where major updates could and did create backwards-incompatible saves. Users had to be careful that files intended for broader distribution were saved in a sufficiently old/compatible format version. Which is to say: this is a sign that the involved technologies are still rapidly maturing.