I completely disagree with the idea. There is more to being evil than having an agressive attitude and an attacking fighting style, as well as there is more to being good that being peaceful and defensive. Ever heard of the expression \"chaotic good\"? And what about \"neutrals\"? As ParaSite said, you can\'t simplify a guild\'s alignment (or a character\'s one) with only two words.
What I mean is, you should be the one that determines the style of your character (as well as the members of a guild determine its style) by in-game actions.
For example, let\'s say I play a Paladin-like character (I know I am talking about characters and not guilds, but I\'m trying to make a point here). Now, he is good aligned, but does it mean he gets a boost on defense? Not necessarily, since his skills and stats depend on MY choices. I might want to make him specially strong so his attacking power is superior to his defensive one.
On the other hand, if I play an Assassin-like character, being him evil aligned does not translate into more offensive power.
I think the same goes to guilds, with the difference that it is not only one person who influences on the style of the guild, but all of its members. Besides, it should be possible to switch styles dramatically (perhaps the leader of an evil guild experienced some sort of enlightment and changed his ways), so being alligned to one side or the other doesn\'t have to restrict the actions of the players.
I probably rambled on and talked about stuff that wasn\'t really the one discussed in the thread, but that is basically my opinion.