[Columbine]

I haven't really seen much of a down-aging trend either or like... massive discrepancies between appearance and reported age. I mean, I don't really know much anime and I don't seek it out personally, but I do frequently come across whatever is being watched by my housemates (4 against 1, we don't watch many nature documentaries to put it mildly) and in most of them the characters look quite age appropriate to me.

Eh, Lemme grab the hard-drive and see what they've actually been watching as I'm rubbish with names.

East of Eden
Persona Trinity Soul
Bartender
Winter Sonata (I remember the LA version of this being advertised everywhere when I was in Japan, I guess the anime is popular too?)
Nodame Cantabile (which must be damn popular if it has it's own donut named after it.)
Beck
Victorian Romance Emma
One Piece
and some beat-up DVD's that I think were Prince of Tennis.

So yeah, I haven't noticed anything, but that could just be that my housemates watch stuff that's aimed at older teens and adults. Well, One Piece is kinda a kids one isn't it? But I wouldn't say it's 'populated by 10 year olds'...