One guild could possibly rule all across the server along with 2-3 other ones,some causing possibly tyranny or pushing around other lower lvl'd or experienced players. Although,even if this contradicts what I just said,I always suggested the idea of one guild having branches and when they have guild meetings,just call the guild leaders,and have them allied to each other.Since,(if they woe)they would have so many people,you'd also probably have to implement an ally system with parties.