Most of the Rev. Gary Davis's songs were copyrighted by Stefan Grossman (quote: If I hadn't done it someone else would have).
Alan Lomax was very bitter because Lonnie Donegan managed to copyright a large amount of Leadbelly's songs - when I heard what Mr Lomax had to say about the matter, I developed a dislike for Mr Donegan. T-Bone Walker lost a fortune because Stormy Monday was copyrighted as "They Call It Stormy Monday", and most of the covers had the title wrong - no royalties paid. People still credit Forty-four Blues to Howling Wolf (C. Burnett), when it was written by Roosevelt Sykes ...
The list is endless!