I can't point a finger as to which country would make a stink over SS partnership, as i don't know the law in every scrap of land on the planet. But if the possibility exists to make a stink, some one will make it. Were the problem is, is that Yoshi-P is calling the performed act "an in game marriage", and as long as it's labeled as such it can never be SS. If it is, then that means that SE is taking a side which would negatively impact the company.
I don't care for either side: for or against SS, my worry is waiting longer then i have to for a game i want to play..
Edit: I doubt minors would care if they can get hitched in a game or not!