I agree with HappySqurriel, in that i don't mind the Friend Codes, but it would be nicer if they were all put into one, rather than different for everygame, i don't think they thought that through very well..
Even then though, it's a one time thing for each game, so i can live with it or without, if it keeps nintendo happy enough to release good online games, then i'm happy to spend probably a *max* of 10-20mins total to add everyone i want to add for each specific game
However, i don't think they should have the MSN system where it tells the person that they have been added, otherwise the FC system is a waste altogether, however they could implement this another way (which may be what you actually meant) by sending a notification that "Johnny has just added your friend code, ask him for his to play online!" (or whatever personal message the user wants to send)
