... the eruption of top incomes that began around 40 years ago need not have solid causes — it could be a case of contagious norms-breaking. This might also explain why movements of top incomes are so different in different countries, with the most obvious determinant being whether you speak English; think of it as an epidemic of broken windows in the United States, which spreads to countries that are culturally close to America but not so much elsewhere.
Emphasis mine. I like that term — "contagious norms-breaking", something epitomized in a Japanese proverb I heard once that goes something like, "If everyone crosses against the light at once, it's okay."
I see behaviors like this everywhere, not just in the actions of the super-rich or super-privileged, so I'm fairly sure it is a major component of human nature. This explains why things like music piracy became so widespread and entrenched, and hard to argue people out of. Why not do it, when everyone else was doing it, and when most of the counter-arguments didn't really amount to anything? Few people respond to moralizing arguments unless they come from someone in authority or from a trusted peer; when they come from some anonymous other, they have no weight.
Now we're reaching a point where free- or low-cost digital music solutions are ubiquitous, and where it's becoming harder to justify piracy because there's far less of a reason to bother. Even there, though, I don't expect piracy to really start dying off for at least another generation or so — not until everyone who bothered with it is offered a workable solution that's at least as convenient as piracy itself, and the behaviors of the whole provide a sense of universal reinforcement.