It was bound to happen eventually. Nintendo has officially terminated all Wifi and online functionality for the Wii and DS family of consoles. That means no more leaderboards, online multiplayer or matchmaking. The Wii and DSi shop channels are still available, for now, so if you wanted to grab some WiiWare or virtual console games you still have the ability.
This shutdown can be blamed on the shuttering of GameSpy Technologies, the server infrastructure Nintendo contracted for their own online systems. Thankfully Nintendo handles the online service for 3DS and Wii U in-house, so they aren't reliant on a third party's servers to keep the lights on.
I admit to being a little melancholy about this. Wii and DS never had the online vibrancy of Xbox live or even PSN, but I still have a lot of fond memories that I made on those servers. I sunk hours into Mario Kart on both Wii and DS, got halfway to prestige in GoldenEye 007, and even had some fun times in lesser known games like Conduit 2. We've seen game servers go dark before for even big series like Resistance, so we all knew this day was coming for Nintendo's consoles. Hopefully those memories can live on in new games for Wii U and 3DS; Mario Kart 8 is only a week away!