Nintendo revealed this snippet of information in an IGN interview with the companys own Entertainment Analysis and Development: Takahashi Tezuka:
GN Wii: What is your plan for the Wi-Fi Connection and how might it compare to Xbox Live?
Takahashi Tezuka: Well, the Wii Wi-Fi Connection works the same as the Nintendo DS one. It's the three qualities that we emphasize. It's easy, safe and free.
IGN Wii: Will it have a central interface a la Live that all games will interact with, or will it be different on a game-by-game basis?
Tezuka: It'll be just like the DS so the interface will depend on the software.
IGN Wii: Will Wi-Fi Connection on Wii also use a Friends Code system?
Ive got to admit that I'm personally disappointed in Nintendo's discission to do this, as the friends code system in my opinion is just plain annoying.
Having to physically type in a 16 character friend code consisting of randomly generated numbers and letters to play against someone you know online is not a fun task, and remembering it is a chore. At the least I believe Nintendo should possibly implement an buddy list system which you can logg into.
Though Nintendo state that by using the friends code system they can keep the Wifi connection free.