The main reason for paying to get into a "Folk Club" is so that the organizers can take limited control of the room. I has nothing to do with the cost or who's on it is to allow for those little subtleties of a live performance.

On the other hand I agree with Captain Crab the pleasure and satisfaction gained in capturing the audiences attention in a bar room situation is fantastic.

Some one on the Mobile Phone learn to walk play and sing and stand right next to them in the audience. The thing I have most difficulty with that I find very annoying is someone coming and standing between myself and the audience in the middle of a performance. Not only dose he or she soak up all the sound but they always manage to distracted the audience so that the lose the plot and story line.

What do you do? Well you do not loose your cool and be polite and smile. I once brought all the Musicians out on strike until the offending customer bought a round of drinks for all the Musicians in the session.