Difficult, really - some performers (because that's what they are, whether they like the term or not) can command an audience, and others cannot.

Whilst manners and courtesy come into it, if a performer isn't 'playing to the audience', they should not be surprised if the audience is turned off.

That said, I agree with those above who point out that it's down to the organiser to set the rules and see that they are adhered to - if someone wishes to chat, they are in the wrong place to do it, as others may well be trying to listen... and, like Joe, being distracted.

I learned many years ago how to command an audience - it's called 'stage presence' - and being obnoxious is not the way to achieve it!!