All societies have got a medium or in plural media, that means institutions which canalize communication and form public opinion. It is often valuable but a one-way street and likely misused. The Greeks learned from the Egypt of the Pharaos that it is bad when medium and executives occur in personal union, too much power in one hand.
Modern Democratic theories and implementations rely on the seperation of powers: Executive (government and police), legislative (parlament) and jurisdicative (court) are seperated. But the power to influence the public opinion is not much controlled, because media are so ethereal, it is so hard to weight them: Not easy to find out who really controls a medium and how much potential it has.
Private media companies became very powerful since the invention of the printing press, cinema, radio and TV, they have become a part of the executive and legislative: Just see the huge PR on election campains, the infotainment and hypes about really knitty-bitty in order to detract the public from the apocalyptic problems of mankind, and the "psychological warfare" treating the own public until it accepts foreign interventions.
If rulers deceive the peasants of facts and intentions we can call it a conspirative act. Since media is nearly the only thing we can rely on for making political decisions, it is most dangerous if they enter a state that corrupted that they can hardly leave it once they´re in it.