It's annoying to have to tell the people who are new to the guild what the expectations are. I agree with the concept of limited guild-broadcast messages, but maybe a middle ground is just to put it as a rule in your guild news (non-leads using guild chat get kicked) or something..? The issue there is that the people who would be jumping on guild chat to talk about their amazing bag lunch for school (or whatever 8 year olds talk about) probably wouldn't know how to navigate to the guild news anyway...