I've been playing over 8 years and had countless cities (more than one on each world, although never two on a world at the same time), and I've been in and out of guilds on most of them. I'm pretty sure that I left almost all of them voluntarily, but there is one I remember that I think I got kicked from. The founder was a clown who didn't want the members doing GE encounters until he said so. Another member and I let him know in no uncertain terms that his rules were short-sighted and foolish, and that he obviously didn't understand the mechanics of the game. At that point either we left or he kicked us, I honestly can't remember which. We messaged all the remaining members, offering to form a guild for them to come to that would not have the foolish rules, but he had them bamboozled and they all stayed. I sometimes wonder if any of them ever wised up.