I guess it would depend on the messages and if the types of messages are limited to the age of all users. You don't want to be playing a horror game, and then have your little sister be the next one to turn on the Wii and go to the Message Board only to find a bloody handprint and a creepy message.
I guess it depends on how the whole Message Board works. Instead of a forum or a strictly controlled and organized space, I keep on imagining it like a refrigerator with messages helter-skelter with magnets or like a board with thumbtacks or like a wall for publicly posting ads. I guess I'd better re-read what it's all about.