To continue with the drifted branch of the thread, I don't hold the view that the tradition is a fixed body of material that should be preserved rigidly unchanged, nor that it's dead. It does keep changing, and new songs get added to the tradition (with alarming speed sometimes) and all the way back through traceable history many of the songs we call traditional have commercial origins, whether it was publication as broadsides or writing for the stage or whatever. The superficial context of some songs is out of date (we don't have ploughboys and knights in armour any more) but the real context of human emotions and behaviour hasn't changed a lot.
Also: with traditional ballads it's impossible to get back to the original "source". It quite correct to say that you shouldn't use a particular tune just because some famous revival artist used that tune, but not because they used the wrong tune and there is a right one: the reason why is that you are free to use any tune that fits, because the traditional ballad singers of long ago didn't have set tunes (or set words for that matter). And broadsides were printed as words, with a suggestion of "to the tune of..." for convenience.
In other words the practice of mixing and matching bits of words and tunes to suit yourself is not some modern corruption of the tradition: it's what's always happened. The only difference now is that with widely available printed, recorded and electronic records available we can see it happening much more readily.
Do we need another thread about this? I've a feeling it's been done already.