I heard someone at our local folk session trying to sing Tommy Sands' song "There were Roses" and when he got to the line about "the tears of the people fell together" - he had some totally different word for "tears" which radically altered the meaning of the song, and made it nonsensical. (So long ago now, that I can't remember exactly what that word was, but believe me, it was so WRONG!) I did have to go and have a quiet word with him afterwards: as politely as I could muster - "Where did you get that song from?" - Answer (as so often) - "Off the Internet". Gaaahhhh!