A copy of Mario Kart Wii will allow you to install the Mario Kart Channel, which can be accessed even when the game disc isn’t in your system. Along with standard features like seeing which of your friends are online and keeping up with their rankings on leaderboards for every track, the Mario Kart Channel will also give you the option of downloading Ghosts and racing against them offline. You can download Ghosts of your friends’ runs if they choose to upload them, or Ghosts of rivals — players throughout the world whose best runs on a track are only slightly better than yours. You’ll of course also be able to upload Ghost runs of your own. And lastly, the Mario Kart Channel will host Competitions, which are special race challenges you can download that are similar to the Missions in Mario Kart DS.

Sounds good to me! =)

More info at the Source

-pwn