Popularised in the 1973 article Dilemmas in a General Theory of Planning by Horst Rittel and Melvin Webber, the term wicked problem refers to a complex problem for which there is no simple method of solution.
Wicked problems are ones for which there is no clear stopping rule – you cannot say for sure that you are done with the problem. Working on it more might well bring forth a better solution. There is no single right answer and every attempt can matter because it affects the things people depend upon.
When the music industry saw downloading audio files as a piracy problem, Apple saw it as a marketing problem. For Apple, the question moved from “how can we stop people from making digital copies of music?” to “how can we get people to pay for making them?” As a consequence they were able to start charging for music that only a short while before was being downloaded for free.