Talk:FAQ/@comment-174.253.165.175-20111007180912/@comment-3991817-20111007181354

As it says in the description of this friend code thing: "You can only specify one friend."

This is because this friend is the one who pointed your attention to the game and persuaded you to install it. At least, this is what the developers mean with it. So it is not strange that it can happen only once that a friend persuades you to install the game :)