Australian Office of Film and Literature Classification (OFLC) doesn't have a rating for video games above MA15+. Thus, if your title is deemed too inappropriate for someone 15 years or older, it's Refused Classification (RC), essentially barring it from sale in the country. Except, it seems, if your game is an MMO.
Our friends at Massively took a look at MMOs in Australia, which -- with few exceptions -- are sold at retail without any rating whatsoever. Developers and publishers claim they've never submitted their titles to the OFLC because they didn't believe it was necessary to do so. That misconception may have come from the board itself, who is said to have given such counsel before it was merged with the Federal Attorney-General's Office. However, the now-assimilated group is saying that MMOs require classification, and selling an unclassified game is a crime. Hit up Massively for more information. This is gonna be a very interesting story to follow.