How do you deal with a heckling audience?

Heckles from an audience can be a performer’s worst nightmare. How do you keep your cool, keep the show on track and handle the heckler with poise and grace?
Shouts from rude audience members and interruptions by mobile ringtones are bad enough, but for many musicians, responding to the source of distraction can be as daunting as the initial antagonism itself.
In the heat of the moment, reactions can range from going red-faced and shouting back a stream of unintelligible noise to just passively ignoring them completely. Only afterwards do you re-run the incident over in your head with your witty retort.
The Independent recently published a piece on performers who had not only managed to come up with a good-humoured response to their floor dwelling nemesis, but incorporated their sharp tongued counters into their performance.
A YouTube video, which you can watch below, of a performance by Slovak violinist Lukas Kmit’s went viral earlier this year. When the grating tones of a Nokia phone punched through Lukas’ recital, the musician, rather than stop playing, kept his composure, creaked out a wry smile and repeated the tune on his violin sending his audience into an applause of impressed hilarity.

Coldplay on the other hand had to stop their performance of hit The Scientist when a fan started playing the tambourine. Lead singer Chris Martin felt he had to put a stop to it.
“This is not a tambourine song – I don’t mean to be rude,” he told the fan after cutting short the introduction.
“Let me be honest with you, we tried tambourine on the recording and had to scrap it – so we have been playing it for ten years with no tambourine. It probably sounds great, but I’m just used to it without tambourine. Don’t take it personally.”
Eager not to lead to negative headlines in the morning’s papers, Martin added: “Don’t take this to be some kind of anti-tambourine rally or rant against the tambourine. It’s one of my favourite instruments.”
He then started up the song again to cheers after promising the fan to “go crazy” with her tambourine on the next song.
The Independent also highlighted one instance where a heckle instigated a musical war of attrition between player and audience.
Last week musician Bradford Cox in Minneapolis was heckled by an audience member to play The Knack’s My Sharona. He then went on to play the requested song, reportedly for one hour.
Sometimes heckles can go well beyond verbal confrontations. Watch the clip below of Nickelback leaving a stage in Portugal after being pelted by rocks!
http://www.youtube.com/watch?v=P7F3O6WYfHQ
What do you do if your performance is interrupted? How have you dealt with hecklers in the past? Have you ever heckled, and can hackling ever be justified?