Obviously, that these concepts are so popular indicates there's a market for them. They're interesting in their own right, and it's always possible to put an original spin on a well-travelled concept. On the other hand, someone looking for a more distinctive guild might struggle to find a good match among all the conceptually-similar ones.

If you're part of a guild that embraces one of these concepts, how does your guild try to stand out from the crowd -- or do you just focus on building a strong guild community, figuring that differentiation will take care of itself?  If you're part of a guild which doesn't embrace one of these concepts, how did your guild arrive at that concept, and are you at all concerned you're catering to a niche audience? And if you're still looking for a guild, how might a guild's concept weigh into your eventual choice? Let us know in the comments!