Unfriended strikes me as a movie that would be absolutely perfect to watch at home, on a laptop.
They shoulda released it digitally, because that just sounds awesome.
HBO survives on subscriptions not ratings, and most of the shows piracy happens internationally.
They'll make their money through merchandise, International TV rights, subscriptions and DVD's (all of which bring in a ridiculous amount of money). They'll be fine. This is more of an issue for international broadcasters.