Unless we are talking about a team oriented game, voice chat should only exist between friends. Mario Kart with voice chat does nothing for me personally, though I wouldn't mind being able to chat with only friends in game. I know not having voice chat in Brawl will suck, because so much of the magic of Smash Bros. is talking smack with your friends.
I completely agree with Deg, I'm not too interested in getting cursed out by 13 year olds who only know the words ****, n00b, ******, teabag and bitch. Chatting with friends would be cool, but chatting with random people from the internets ... no thanks.