The ESRB's Adults Only rating for Rockstar's
Manhunt 2 was always going to hurt the game in U.S. retail. That hurt has now, apparently, become terminal as Sony and Nintendo have declared that they are both refusing to allow the game to be released on their platforms.
Microsoft has also declared that its policy is to ban AO-rated titles from the Xbox.
Sony's statement reads, "It's currently our policy not to allow the playback of AO-rated content on our systems."
Nintendo states, "That's why the ESRB provides ratings to help consumers understand the content of a game before they purchase it. As stated on Nintendo.com, Nintendo does not allow any AO-rated content on its systems."
Therefore, it appears that a rating of AO does not mean "Adults Only", it means "Access Omitted".
Source: Gamespot