I have a different viewpoint from Earl, dick greenhaus and Bert. Folk tunes are, by their nature, very versatile and you could get away with playing them in many different styles without losing the sense or the feel of the song. What I'm saying is that the nature of folk songs is that they are adaptable. In a way I think its apt that they do get re-vamped to entice another generation of listeners because, after all we're talking about music for the people.
The key to the success of the more famous 'Folk Songs Revisited' (in my opinion) is that they are done with a lot of thought, a great deal of talent and most importantly, originality. The performers bring part of themselves and their influences to the song, changing it but without destroying it. Examples that come to mind are 'Scarborough Fair' by S&G and 'Whiskey in the Jar' by Thin Lizzy.
I also like to hear incorporation of folk ideas into modern tunes. It is these sorts of combinations that lead, inevitably, to new and dynamic styles and forms of music. We have to look forward as well as back.
Laoise.