Same thing with guilds, really. You have casual guilds, raiding guilds, pvp guilds, rp guilds, and combinations of those. There will be pvp circles, raiding circles, rp circles, etc. In GW2, you can be part of multiple guilds at the same time (but only rep one at a time). This was a similar implementation. It generally aims to increase the number of people you can play with, not decrease it. Of course, cliques can (and will) always form and can be harmful, but a circle, much like guild, can't be open to everyone bc well, it would end up defeating the purpose of a "specialized" grouping like a circle. Some circles might have a jerky attitude, others won't.