The parlay rule is very useful in MOUT situations, not so much in outdoors play. This past weekend I attended Op Irene at Fort Knox, Kentucky. I personally witnessed several parlay situations in which members would enter a room quickly enough that the players would be standing barrel to barrel. To be fair they called each other out and accepted that it was good movement or good placement overall then continued on their way.
All in all the parlay rule only works if there are mature players.