1UP is reporting on an interview with a GameSpy PR bod, who has stated that Wii friend lists will be title specific. This could mean that, if you want to play online against somebody in Pok√©mon Battle Revolution, you'll need to write down their friend code and then type it into the Wii, but if you try to play another online Wii game, then you'll need to enter yet another long code. However, not many details were given, and friend codes were not specifically mentioned in the original interview, only game 'rosters'.
The extract below is from the interview with an unnamed person from GameSpy, done by a blogger named "Falafelkid"
Falafelkid: Just one last question to make absolutely sure I have got this right, please. If I have a friend roster in one game, that roster will not be available to me in any other game. I have to build up an entirely new list for each title, right?
GameSpy: The answer to your question is yes, for the Wii friend lists are game specific.
It's been expected for a while now that friend codes would be abandoned for the Wii - after all, with each Wii having a console specific number, it would make more sense for Nintendo to get users to add friends with this number. We'll wait for more details to arrive, so check back with PALGN for all the latest.