Well it seems that Left 4 Dead 2′s is not kosher for the Aussies. The content exceeds the allowable rating of MA15+. Any game the goes above this is basically considered banned.

From the offical Austrian report  “The game contains realistic, frenetic, and unrelenting violence which is inflicted upon “the Infected” who are living humans infected with a rabies-like virus that causes them to act violently. The player can choose from a variety of weapons including pistols, shotguns, machine guns, and sniper rifles. However, it is the use of the “melee” weapons such as the crowbar, axe, chainsaw and Samurai sword which inflict the most damage. These close-in attacks cause copious amounts of blood spray and splatter, decapitations and limb dismemberment as well as locational damage where contact is made to the enemy which may reveal skeletal bits and gore.” So this basically means Austrialia won’t allow it citizens to play it. This is coming from the country that has insane gun control laws so not surprising.