Sorry. Really. OK, I'm not sorry, Official Nintendo Magazine are, for all the confusion. Seems the news that Mario Kart Wii would feature 16-player online play wasn't news at all. It was speculation on their part:
The details printed in Official Nintendo Magazine 21 regarding Mario Kart Wii were healthy speculation on our part and are in no way an official announcement from Nintendo.
We are sorry if we have mislead anyone. We do not set out to mislead our readers. ONM apologises profusely for any misunderstandings that this has caused.
Rest easy, Wii owners. The hassle of having to punch in fifteen friend codes has been averted. For now, at least, since there's always the chance ONM published something they shouldn't have, and that this will be announced during TGS in a couple weeks time. More players for online battle than expected? Update: Official Nintendo Mag reponds [Games Radar]