Before my very first lesson, my instructor took a decent amount of time to go over the safety concerns before he ever turned on the engine. By the time he went to start the engine, I knew the basic safety principles, such as securing the plane prior to starting is, standing behind the prop, and never ever reaching for anything close to the prop. I also knew what the wire hanging from the glow plug was.

Please don't take this the wrong way, but in the spirit of having a discussion about this topic, I'd say the onus was upon you (the more experienced modeler) to brief the inexperienced about the very basic safety concerns prior to starting the engine. I am very glad nothing happened, but next time you show off your plane to a rookie, you may want to spend a few very valuable minutes and go over the things we have learnt and may take for granted.

Other than the little fright, glad there was a happy ending here!