Certainly where a guest is booked in a folk club it can cause problems if the MC feels duty bound to put on his/her regular floor singers/audience /supporters of variable experience/talent ~ the state and constitution of the club can a limiting factor!

Frequency and venue of the club will also have a bearing on how the night is configured and expected quality of the paid for entertainment and of course the audience knowledge and expectations

Joining in with choruses can be off putting if not in a familiar venue, for audience members who are not expecting it!!

Ray