See other failures under 000.html.
Broken Giant TCR C2 frame. From http://www.bikeforums.net/showthread.php?t=451756 as of 2008/08.
I was doing right about 20 [miles per hour]. I was on a narrow road and I kept getting pinched to the right side by people that didn't seem to notice that there was an open lane. I saw that there was a guy behind me that was patiently waiting so I pulled as far right as I could and waved him through. He passed and then [a pothole appeared]. I hit it and the frame cracked, I endoed and slid for a lot longer than one should slide at 20 mph. Half my body was in the grass while my head/torso were on the road.
Service history is unknown.
Although the failure is the result of an accident, it is notable that the frame failed catastrophically (completely and with dangerous results) before other parts. A more typical failure with metal frames is rim damage, steer tube bending, or buckling but not separation of the frame.
To over-simplify slightly, carbon fiber has a smaller difference than metals between the load at which things start to get damaged and the load at which it fails completely. Designers thus have a range of choices including "starts to fail at the same load but fails completely at a lower load" and "same load to fail completely, much higher load before it starts to fail." Weight is important for bicycles, so it is tempting to design for the same "starts to fail" load, but note this can lead to more severe injury because "starts to fail" loads are sufficiently common.
See also FAIL-107.html.