Ranking systems dramatically increase the competitive atmosphere of a game. You can't help but compare yourself to everybody else or worry about rank.
Further, people treat you differently because of your rank. Many will skip out on a match if they don't like the rank of their opponent(s), and if you're doing teams, people boot their low-ranking team mate.
Unlike many places where you can easily appeal to both the casual and competitive crowd, rankings are one place where you have to choose one in exclusion to the other, and since online won't be good for competitive matches anyway (even Sakurai says it will be laggy), they made the right choice. And BTW, I say this as a competitive player.
Quoted. For. The. ****. Truth.
Seriously, in a game as frame-intensive as this one, even the slightest amount of lag is enough to screw with the outcome of a match. Seeing as how no two people will ever both have perfect connection rates,
THERE WILL BE LAG IN ONLINE MATCH-UPS, PERIOD.
That, and there
WILL be cheating of all sorts. Maybe not in the beginning, but eventually, as the Gamesharks and Action Replays for Wii start coming out, people will be using crap like No-Damage cheats, One-Hit Kills, and Player Two Always has 999% Damage hacks flooding the system. Beyond that kind of flagrant, over-the-top cheating, is more subtle stuff like padding wins and once you have a decent enough record, refusing matches with anyone you even
THINK might beat you, thereby completely defeating the purpose of an online leader board in the first place.
It's happened with
EVERY SINGLE ONLINE-ENABLED game thus far, and anyone foolish enough to think it won't happen with Brawl, is sadly deluded. That's why I'm glad that only Friend Code matches will record wins/losses, that way, it will be easy to track cheating scrubs like that and avoid them like the plague that they are.
Besides, it's not like it's necessary to enjoy the game with, so why worry so much about an arbitrary number underneath your name? Kinda like Post Count, wouldn't you say?