I heard from my wife just the other day that the woman in Japan does not have to change her last name to that of her spouse when marrying a foreign national anymore. Whether it holds for Japanese women marrying Japanese men I do not know.
As far as I know, what Mikawa said is also correct. In the cases of an only female child the husband will often adopt the wife's family name, if he has other brothers, in order to keep the family name of the wife going.
My wife is an only child, but since we never had any children, I see no reason to change it even when we do move back to Japan. But if I had to for some reason or another I would not be against doing it.