"probably has a wide safety margin"
probably being the key word. I have found, as a clyde, that I have reached the safety margin with nearly all of my bicycle components. The issue with carbon fibre (and Ti, and Al) is not that it is inherently weaker, but when you reach the safety margin, it breaks catastrophically, not slowly like steel. Technically, you want something that is ductile, with a yield strength (point at which it bends) is much lower than the ultimate strength (point at which it breaks). With a steel bike (or fork), if your too heavy, it will bend and gently let you know to "please get off me", carbon, Al and I believe Ti are not very ductile, and so will snap before you know there is a problem. This is what makes them scary for me. I ride an all steel bike, including a steel fork. I sometimes wonder if I am in idiot for doing so, since EVERYONE else is on carbon, but this is just a test of the common query, "if everyone jumped off a cliff...." I get to thinking I should try carbon, and then my Al crank cracks or something ridiculous and I am again reminded that bicycle engineers are for some reason unable to fathom the existance of riders who weigh more than 180lbs. (I am 250lbs)