It definitely pays carefully inspect props and spinners from time to time. I have had high-time wood props chuck a blade, but the vibration resulting from a relatively lightweight wood blade usually doesn't do all that much damage. Two plastic prop blade-chucking episodes nearly wrecked my model each time - servos were all out of their grommets, horizontal tail came unglued, etc., resulting in barely-controlled crash landings, and neither prop had experienced any previous damage.

While I was helping another modeler tune his engine, his plastic spinner flew off, bounced off the ground, and hit me just over an eye, producing a nasty cut. It could have been much worse - and I was, as always, standing well out of line with the arc of rotation.