Hannes Coetzee it appears, from South Africa. Interesting. And as soon as you see it you can't help but want to grab a guitar and a teaspoon and try it. But I don't think the tricky bit would be the crick in the neck, it'd be the strain on the teeth.

Of course the other way to do this kind of thing would be to call in a mate and play the guitar as a duet instrument.