Not surprised by the results at all, but I do feel there are definitely even more 46+ ...just not on the forums.
As for telling age...It's not necessarily that someone will track us down with our age, but saftey for the younger players.
I don't really have a problem with telling my age personally... My friends here know my age, mostly told outside of the game. HOWEVER, we do have some younger players. Some are even younger than 12. There are too many creeps and bully's that will see that someone is a young player and take advantage and manipulate them. It's not as difficult or as rare for this to happen as you think it might be. Sure we might like to think we have a responsible community and parents monitor their young children when online, but that's not the case.
I've played quite a few online game and age has always been considered personal info.