Overstress a metal component it will deform
While this is true for most parts on a bike it wont deform very far before it snaps and you have to notice it first before it fails suddenly.
If you want to see carbon fiber standing up to rock impacts etc then look at rallying.
I have carbon bars on my bike and they are now comming up to 5 years old and still have faith in them.
I like how carbon never feels cold like metal.
The carbon forks on my commuter have stood up to me hitting a huge pothole at speed that took out both of my tyres with out a mark.
The only thing that has stopped me from getting a cf frame is cost though they way things are going at the moment cf is coming down compared to steal/alu/etc.