Doesn't matter, wouldn't be any for Nintendo. It wouldn't hold up in court at all and probably wouldn't get anywhere. It says on the front of every online playable game box "Game experiance may change online".
Not all cases end with the judge awarding attorney fees to the winner of a case, even when it's cut-and-dry.
And it's not just legal issues. I don't know if you saw this, but a few months back Dateline (or one of those other TV news magazines) did some report on how people could use the DS's PictoChat to lure children into pedophiles' grasps. Nintendo may be being paranoid, but their family-friendly image is very important to them, and it's not unfounded paranoia. Even with nonsensical safety measures in place, the news media is going to find a way to do that sort of thing. And yes, I realize that it's mostly just ignorant people who pay any attention to television news, but Nintendo likes to get money from ignorant people as much as they do from anyone else.