http://www.bustedcarbon.com/

What happens when you crash big time at 30mph or more. But then again a high performance bike is designed to be ridden at high speeds.

http://www.youtube.com/watch?v=-RNAYR3KPIg

shows Mark Cavendish getting involved in a crash at 40 mph.

Carbon will break, but so will any other kind of frame when it is subjected to abuse. I've seen steel frames get broken. The newer carbon frames are very strong and as long as you're not racing or hitting potholes and generally riding like an idiot then there's no reason why a carbon frame won't last as long as any other.

I had people who have had some of the early titanium framed bikes say that they had metal fatigue problems because of excessive flexing in the chainstays.

I've seen steel framed bikes literally fall apart because the welds popped.

All the local LBS have told me that the failure rates of modern CF frames is about the same as any other frame.

Carbon composites will tend to break or shatter when they fail as opposed to bending then breaking. I've got a pair of CF x-country ski poles and I would never give them up. They're probably more reliable than any metal poles I've used.

My youngest son is a 15yr old who happens to be into freestyle skiing and he's managed to literally destroy a couple of pairs of $120 ski poles in one season. A broken metal pole or bike frame is probably far more dangerous in a crash than a carbon fiber one so I'm looking at getting him some carbon fiber poles (for about the same price as metal) not just for strength but for safety reasons as well.