I personally don't see why the maxim of "better safe than sorry" is not adopted considering the cost of props in proportion to the cost of modelling gear in general. Even if you could get away with not losing any money (because of insurance) if you or someone was injured by an "exploding prop", could you live with yourself if your prop hurt someone else when you knew it was damaged but you flew it anyway?

You are going to think I'm stupid but I flew a 40 powered plane a few months back with a perfectly good prop but a plastic spinner with a bit of a crack in it. I thought it would be fine - was too lazy to drive to the model shop to get a new one, so I took off, and Bang, the spinner hit the prop as half of it exploded and made a sound like a good shot with a baseball bat. This was full power - prop was a 10 6, engine was an OS 40. Luckily the plane was 20 feet up and away from the pits - if that had happened on the runway as it was on take off run and someone had got in the way then it might have been nasty.

So lesson learned - safety considerations are no place for optimism.