In the current game I'm running the following has happened. I have a party where one character is good (neutral good to be exact), and the rest are either evil or nutty in the case of the gnome warlock. I'll mention the party is composed of a Mystic Thergue (I've likely spelled that wrong), Lawful Evil Fighter, Lawful Evil Cleric, Chaotic Evil Assassin and a Gnome Warlock who while not evil is always causing trouble.
However the MT is played by the best player I've played with and he's the party leader. They all follow him as he's saving the party's bacon all the time and he's quite smart (the player) and he knows how to lead. So the fighter (who is very powerful himself) follows and the cleric who is tied to fighter through worship of the same god follows the fighter. The assassin is new to the party and he'll do what the fighter says. The players are all very good, but the MT's player is another level above...so I'm left having to balance things hoping each session goes well without too much chaos.
The problems are minor, but any input would be great.