One of the problems with profession sport is that coaches are bastards. Get rid of the penalties for encroaching on the mark from behind, and Clarkson will have a guy jogging behind the kicker (or running 5m beside him) every time. Technically he wouldn't be affecting the play, until the bloke plays on, in which case he lays a tackle. If the umpire shoes him away, all it does is slow down the game which disadvantages the team who won the ball.
Yeah, they probably were overly officious tonight, but lets not let the players off too lightly. It's not that hard to avoid running within 10m of the bloke with the ball. NicNat made it 5 or 6 years in the league without ever being within 10m of a guy who marked it.