Just wanted to pop in here in case -theCHUD- or anyone else interested in this game comes around. No, you do NOT need 4 players to play Four Swords. You can use 4 players, but the game will still start just fine with only 3 players or 2 players, and the levels will arrange themselves so that you still have enough Links: Statues appear to hold down extra buttons, blocks are only as wide as the number of Links you have, and so forth. So if you only have 1 friend who also has the game, that's enough to start playing.

What aggravates me is how the game doesn't make it clear that you could play with only 2 or 3 players instead; as shown on this thread, people will start up the game, realize it needs more than 1 player, then assume that it requires exactly 4 players because after all, doesn't the Four Sword split Link into four? But it turns out Link doesn't need to use the Four Sword's full power if he doesn't want to!