Some people seem to be confusing the RBDM concept with a Psychopathic DM.
A RBDM does not commit the innane murder of PC's in senseless traps, or with weird monsters out of the blue that are immune to everything.
A RBDM paints a fantastic picture, detailing events and happenings along the way, tagging the PC's along on the story, only to hit them with a whammy at the end, which, when they stop and think about it, leaves the players with the feeling that they should have been able to see the whammy coming, had they only paid attention to the detail. Instead, the PC's realise they have doomed themselves, by their own choices.
A true RBDM leaves the PC's frustrated, and the players demanding more.
A RBDM leaves a PC with a terrible curse, a horrible fate, one that was self-selected by the player.
A RBDM provides the rope with which the PC hangs himself, while the player applauds.