It's all a matter of taste! Personally I don't chew Gum however if I was performing "I'm for ever Blowing Bubbles" I would.

I know one performer who sticks his Chewing gum onto his beer glass before doing his set. This simple act prevents other from accidentally stealing his beer and clearly identifies the glass as his. Who am I talking about! " Bernard Wrigley" who else!

I would suggest that whatever a performer doses on stage should be mirrored in the amount of applause that they receive.