Back in around 1950 the later Labour MP and Cabinet minister Tony Benn was training at the BBC and required to come up with program ideas. One of his was You the star, in which a radio drama would be broadcast with the leading part left silent. The words for this role would be published in the latest edition of the Listener so that the public could act out the leading role for themselves.
The idea never made it into production, quite likely in part because as Jad Adams puts it, “Perhaps [the public] would find themselves without a copy of the magazine, listening to a very avant-garde radio play”.
But it does go to show how user-generated content and audience participation have far older roots than is sometimes remembered.