Hope you've already gotten all your Dragon Quest IX treasure maps and downloaded all those daily Professor Layton puzzles. If not, now's your last chance.
At some point in the next 24 hours, Nintendo is turning off online functionality for Wii and DS games including Super Smash Bros., Mario Kart, and Pokémon. You'll no longer be able to use the WiFi on Wii and DS to play those games online, download new content, or access leaderboards.
(Nintendo has a full list of all the games that will be affected.)
You'll still be able to watch video services (like Netflix) and access the Wii Shop, but alas, no more Dragon Quest treasure maps for us.