Perhaps so, jag, but going back as far as we can the folk have always borrowed from popular music (just as popular music occasionally borrows from folk), and we also have to remember that musical genres overlap so it's best to picture this in the form of Venn diagrams rather than something with hard and fast boundaries. There are those who want to say 'this song is a folksong because of blah blah' and 'this song isn't a folksong because of blah blah' but it's not as simple as that with every song in the canon. Some songs fulfil all of the criteria and some only fulfil some of them.