The Australian government has released this draft document (Adobe Acrobat format) with "Guidelines for the Classification of Computer Games," in anticipation of the adoption of an R18+ rating for video games down under. Word is: "Violence is permitted except where it offends against the standards of morality, decency and propriety generally accepted by reasonable adults to the extent that it should not be classified. Sexual violence may be implied, if justified by context," and that: "Sexual activity may be realistically simulated. The general rule is 'simulation, yes – the real thing, no'." There's analysis of this on Gamasutra, where they note that a vote on the new guidelines is expected in July.