If they do it every time, the opposition should be able to defend against it. They would only have to have it rubbed in their faces a couple of times and they'd stop doing it. I remember back in the 80s when Parra used "The Wall" -- three players would stand in a line, shoulder to shoulder, one of them would receive the ball from the dummy half who would then run behind it. The defense couldn't tell who was about to get the ball. It was barely legal but within the rules and they never failed to use it every game. One day at a game against the Bulldogs at Belmore Oval, Geoff Robinson just shoulder-charged into it, sending blokes everywhere. It was never used again.