"I think that the folk tradition is fueled by bad memory and laziness... not seriously deliberated rewrites."

And that's the way the great songs got knocked into shape over the years. And knocked out of shape too,because it works both ways.

But the happy accidents probably have more staying power. If you search out an 18th or 19th century broadsheet version of a song that survived into the oral tradition, it seems to me that the version collected in some workhouse in Edwardian times always seems to turn out to be far improved.

And that process continues.