“Here be dragons” is a phrase used to denote dangerous or unexplored territories, in imitation of the medieval practice of putting sea serpents and other mythological creatures in blank areas of maps. (Wikipedia, Here be dragons)
As a reaction to the Utopian science fiction (frequently set into a distant glorious future), cyberpunk projected all our fears into the uncharted territory of the very near future.
What separates us from the near dark future is a kind of unspecified, yet imminent apocalypse. Hence, most of the cyberpunk scenes are post-apocalyptic ones, where the apocalypse is a given, part of a forgotten history:
“…no one today remembered why the war had come about or who, if anyone, had won.” — Do Androids Dream of Electric Sheep (Chapter 2)

