Now I know what you guys might be thinking: It's just Friendcodes, not too much trouble, right?

WRONG. For a game that is supposed to have 16 player multiplayer, this just will not work period. Think about it. Is Nintendo expecting us to input fifteen long codes for Wi-Fi multiplayer?

High Voltage Software had this to say:
High Voltage insists it's going to lengths to make this process as easy and streamlined as possible. But it points out that this is Nintendo's field and they have to play ball on it. Although the two designers interviewed said they are no fan of the codes, "it's [Nintendo's] console, which we have to have their permission and their sign-off for whatever we put into the game. And if Friend Codes are what is, [that's what it] is gonna be."

I for one will not be purchasing this game if Nintendo insist on having their 'safe' way with us. I thought that Nintendo had eased up on player to player communications with the advent of WiiSpeak, but it looks like I may be wrong.
On a related note, Nintendo itself are rumored to be publishing The Conduit, which will almost certainly help to maximize the game's sales potential.

Source: Conduit "Probably Will" Use Friend Codes