[sailingdog]

Saying that the carbon fiber masts on a racing boat broke, makes them a bad idea for all boats is generally a bad generalization to make. Racing boats generally have lighter masts for the size of sail than do production boats. Racing boats also generally have lower safety ratios than do cruising boats, and are generally pushed harder, so are more likely to brea hardware.

The early carbon fiber bicycles were made when the fact that carbon fiber tends to be very unidirectional in resisting forces wasn't really understood... and that lead to bicycle frames that would collapse under the stresses of cycling if the frame was scratched in the wrong place. That really isn't the case anymore, since the material has been used for decades now, and is fairly well understood now.

JeffH mentions the issue of lightning strikes... the problem is that graphite is relatively good at conducting electricity, but the laminate heats up quite a bit if exposed to a high current and voltage, and the heat can cause the spar to delaminate internally, where the damage is not going to be visible—leading to sudden, unexpected spar failure.