I, like a lot of players just want friendlies to be set that both managers have to agree on the match before it goes ahead, ie one requests a friendly and the manager would get a request then agree to it or disagree to it before the game is allowed to be played.

To make it easier for some you could do it so the player who receives the friendly request gets a facebook notification and/or a notification on mobile phone like we get 5 minutes before a game is about to start.