Posted from IGNDS mailbag:
I've been playing around on Mario Kart DS since this weekend with very few problems. I noticed on the message boards that you snoopy-snoops have been peeking around Nintendo's Wi-Fi website, and yes, my name (CraigIGN) appears showing that I'm blasting through the races against the world. Or at least, the world that's currently connected and having a copy of Mario Kart DS.
The problem with Mario Kart is that the online portion is extremely limited. The only way you'll be able to connect with me on a regular basis, outside of randomly connecting to me via "Worldwide Mode" is if you have my 12 digit Friend Code, and I have yours. If you have mine, you still won't be able to connect to me as a friend since I don't have yours. Knowing someone's online name isn't enough. Nintendo's system also forces the group of up to four players -- people can't choose who to play, or even enable a simple two or three player challenge. And even in random Worldwide match-ups, if I enjoyed racing against someone, I have no way of adding that person to my list of friends. There's no way of chatting with that person or finding out his email address to get that information after the fact, either.
Get Mario Kart DS because it's the best freakin' kart racer ever, with an incredible focus on single player and local multiplayer. Don't get it solely for its online component because you'll end up wanting way more than what's offered here.
-- Craig