In theory, order shouldn't matter, right? But I recall seeing this trick for adding comments to json:

  { 
    "foo": "this is a comment about foo",
    "foo": "actual value of foo that overwrites the comment"
  }

The trick is that the second value value of foo overwrites the first. But, clearly, sorting would would wreak havoc here (if the value was used in the sort key). ;)