I have seen prophecy as a plot device discussed on here several times as a big no no basically. The reasons given make sense, yet...It is used a LOT, especially in fantasy. I've also seen an equivalent device used more than once, such as fortune telling. So, my question are, If prophecy is such a weak plot device, why is it used so often? Under what circumstances does using prophecy work? Enhance the writing rather than look like a band aid to explain the unexplainable? etc.