There is a ‘Community’ feature within Mario Kart 7 that hasn’t been explained with an amazing amount of clarity so far, but Nintendo has provided the following explanation:
The new Community feature allows players to create groups with other Mario Kart fans while setting up specific rules to make customized racing environments. Easy setup allows players to quickly create a community and share with others via the StreetPass™ feature. Community leaderboards will also show the most up-to-date information from recent races.
They’ve provided much clearer details though about the StreetPass functionality:
Walking by other Mario Kart 7 players in real life with StreetPass enabled allows gamers to exchange racing scores, win/loss records, number of collected coins and other game data. With SpotPass enabled, players will be able to receive ghost data to race against. Up to seven ghosts can be downloaded at the same time, allowing for a full eight-player race.
This was already a game worth being excited for, but it’s really becoming something special.