Well, what can i say? I like alliances, but they are of no use, if the members hardly know each other and can therefor not really trust each other. Sure, the more neutral guilds are allied, the more power the alliance would gain, but then again the bigger the alliance, the harder it gets to make decisions and to control the whole thing.
So what is it i want to say? Alliances are a good thing as long as they are not too big, have a purpose and are close knit.