The Smash Brothers Dojo announced the details about Wi-Fi play today in Masahiro Sakurai's blog. The announcement reveals the ability to play online with friends via friend codes, which is exciting in and of itself. There is also the ability to play online vs random opponents however, which is absolutely awesome. Now if you want to play Smash Brothers at any moment you will need only to plug in and find a game!
Some critics have already started harping on the drawbacks of the system. In the friend play mode you are able to communicate, but Nintendo is very worried about abuse due to their young audience and the air tight reputation their company has for family friendliness. As a result of this concern they have disabled the ability to communicate with enemies in the random online games. You won't even be able to know the name of your enemy. The theory being spouted on forums is that this is the equivalent of playing vs bots, but bots don't get exceptionallly good at the game and are easy to beat when you know how. Beating a bot is all about learning it's programming and takiing advantage of the shortcommings. Playing online vs real living enemies is supremely preferable to playing against bots, even if you can't chat with the person you are playing.
Using a Voig team page to organize online players and share friend codes is also a very viable way to build a community of online Smash Brawl players. Once you join a large social group that plays together online the possibilities for tournaments and organized play are endless. I'll be getting a Wii just for this!