If Bandcamp were to try such a move they would destroy the value of their business overnight. Retroactively changing the agreement with your customers about their IP is the best way to permanently destroy trust.
It would be a more dramatic overnight loss of customers than Unity. It's entirely laughable, and given that laws restrict the licensing and royalties of music, it might not even be legal.
Labels can only write up contracts giving them rights because they pay for studio time (given them a financial buy-in to the creation of the music) and pay advances against royalties. Not so for indie distributors. I don't know if there are specific applicable laws, but it's absurd enough that everyone would immediately drop Bandcamp.
Music royalty rates, for physical records, radio and internet streaming, are also determined by a panel of judges: the United States Copyright Royalty Board.
Labels can only write up contracts giving them rights because they pay for studio time (given them a financial buy-in to the creation of the music) and pay advances against royalties. Not so for indie distributors. I don't know if there are specific applicable laws, but it's absurd enough that everyone would immediately drop Bandcamp.
Music royalty rates, for physical records, radio and internet streaming, are also determined by a panel of judges: the United States Copyright Royalty Board.