Nintendo has announced that on May 20th of this year they will be ending online "functionality" for many Wii, DS, and DSi, titles. This isn't too surprising and is most likely just a tactic to get people to move to their more current consoles. Unfortunately their more current consoles haven't sold like they have hoped so maybe this helps out a little until they can get something new into the market. Wired has the story.
Nintendo is terminating "certain online functionality" for the Wii, DS and DSi including online play, matchmaking and leaderboards for many of its games.
The functionality is offered via the Nintendo Wi-Fi Connection feature and its removal on 20 May will affect games including Mario Kart DS, Mario Kart Wii, and Pokémon Black and White.