Hellbanning (aka ghost posting) essentially dupes someone into thinking a system is working for him/her when in fact things are being faked. From the NYT article: "The company [Uber] then served up a fake version of the app [to law enforcement], populated with ghost cars, to evade capture." The linked-to Quincy Larson article is more to this point, describing Greyball as a tool that allows Uber to "figure out who's likely a cop, then 'hell-ban' them from being able to use Uber."
Duct tape is like the force. It has a light side, and a dark side, and it holds the universe together ... -- Carl Zwanzig