The Steyn incident. Images extracted. Does that look if it hit the ground straight down or forward?
Without seeing where and when it hit Steyn's hands and where it bounced it's difficult to tell from those still shots. I watched a replay in motion and it was a knock-on for me.
CD brings up an interesting point here over which I've often pondered. A ball may hit a player's outstretched hands and then fall BEHIND the vertical to the ground, ie. not towards the opponents' goal-line. However, these would be very rare instances as players running forward at speed, as Steyn was, invariably propel the ball forward as they touch it, making it a knock-on. I imagine referees would have some difficulty carrying a piece of string with a bricky's plumb weight to ascertain the line of fall; they'd have to call a halt in play to determine the spot where the ball touched the player as well as the exact spot where the ball hit the ground. In the interests of accuracy I feel the various referees' associations should make arrangements with their local Bunnings to have all refs issued with string and weight. We also need eagle-eyed video operators who can assist refs to determine the exact spot where he should hang his string. The VO's assistant could then simultaneously mark the spot where the ball touched the ground and, with a tape measure, declare it back, or not. I could confidently say about 0.05% in cases when the ball fell in front of a player would be found to have been inaccurately adjudicated.
When I did my initial referee's course this possibility was touched upon; the wise convenor suggested ALL instances of the ball going down in front of a moving player should be called knock-ons. I'm still perplexed why the three officials at Loftus didn't see it that way.