I swear, the next person to talk about how this game needs to be online should be murdered...
With the way the game is set up being cooperative and competitive at the same time, if you put this online where you can't punch or yell at someone for being a ass the game would quickly degenerate with one guy hanging out at the end of a thin bridge with the fire rod burning anybody that got close and knocking them off or something similar and would cease to be fun really fast, often even if they ARE your friend.
The thing is in no way, shape or form designed to be online and you don't have to look any further than all the crap people have to do to online multiplayer game design to avoid things like this to understand why it simply would not work.
EDIT:The game is the best friggin' party game since SSBM and it should stay that way. PARTY game.