Total Paparazzi, Law enforcement, and Military, and perhaps some scientific applications. This is where I see the bulk of sales for these lenses. And of course the few (100's? 1000's? ...maybe) well-heeled serious enthusiasts. And some pros - a few. For example, far safer to photograph Kodiak bears as well as Polar bears from a distance: at 1200mm you can double your distance to subject and still fill the frame... ;-)