Here is the article in question about the new guitar hero from joystiq.

Guitar Hero World Tour can save DLC to an SD card

Posted Jun 21st 2008 12:00PM by JC Fletcher
Filed under: News, Interviews

Vicarious Visions' Karthik Bala has once again confirmed paid downloadable content in the Wii version of Guitar Hero World Tour, though current Wii guitar games have left us doubtful of any feature. Furthermore, you'll be able to save your songs to a "Rock Archive" on an SD card, and even play songs from the card without copying them over first. But ... but isn't that completely impossible?

Bala also confirmed that despite the new guitar's wacky gimmickry, your old Guitar Hero III (or Guitar Hero: Aerosmith) guitar will work just fine, and that "any USB microphone should work." With all these features, Vicarious Visions is going to have to be really creative if they want to disappoint.

SSBB already does this... This doesn't confirm anything.

Well this shows there is a solution for DLC.

SSBB has to copy to the wii first temporarily which means is not directly playing from the Sd card.

Wow..... I don't know that I can play music from SD card while playing Excite Truck & Endless Ocean either....

 I say this again those game do not allow direct playing from the SD it copys on to the wii  temporarily and then plays the music which game if you read the article does not. Think about if you were already to play form sd cards directly people would not complaining about transfering games back amf forth.

They allow playing data directly off the SD card not games. This is nothing new and just like excite truck. This does not confirm playing a game from SD, only some game content which has already been allowed such as excite truck. You will still need the game dvd for the main game.

This confirms nothing new for SD support. The transfer rate of an SD card is fast enough for songs and has always been. That doesn't make it fast enough to play programs from that do not fit entirely into memory. You are confusing data files with program files. At least some VC games should be small enough to fit entirely into memory, but obviously it's the larger ones that will be an issue.

edit**

Did you just pull that out of nowhere? What proof do you have of Excite Truck and Endless Ocean not allowing direct play from an SD card? Source?

I thought the Wii already did this with some games.