There's an old wives tale in the general aviation that's actually not a wives tale at all: If you get into an oscillation on landing and don't get out of it, the propeller will strike the ground on the "down" portion of the third up-and-down cycle. I've seen it happen on several occasions.
Here's the setup: Pilot lands hard; the aircraft bounces back up into the air, a combination of landing gear spring forces and ground effect producing more lift. The pilot then pushes the control column forward to get back down to the runway. Unfortunately, that's the exact WRONG input, as the energy then increases again and continues the oscillation.
The right input, at least for a single-engine piston driven aircraft, is to either do a go-around after that first or second oscillation, or, if there's enough runway, hold the control column aft (up elevator) and let the energy bleed off before the aircraft settles again. Once on the ground, keep the control wheel back and take out the flaps.
What should this Korean Air pilot have done? Looks to me like the control column was cycling fore and aft, promoting a pilot-induced oscillation and there doesn't appear to be a go-around attempt. Thanks to FlightAware.com for heads-up on this video. I'm just saying... NOTE: The original video has been pulled from YouTube, but you can see the clip here...