Did We Get the Robert Johnson Myth Completely Wrong?

All guitar players know the legend.  An unknown blue guitar player meets the devil at a crossroads at midnight somewhere near Clarkesdale, Mississippi, and offers to tune the young man's instrument in a special way.

"This will make you the greatest blues player in the history of the world!" Satan said.  "All I ask in return is your soul."

The guitarist, with nothing to lose, agrees.  He's handed back his guitar and Robert Johnson ends up becoming on the most famous bluesmen in history.

But what if this entire legend is wrong?  Forget dismissing the supernatural elements of the story.  What if this whole thing is based on the wrong Johnson?

That's the contention of a documentary from NPR.  Fascinating stuff.