A poorly built frame will be bad no matter what material it's made out of. They use glued carbon fiber joints to hold the wings onto jet fighters. The leading edge of the world's first SCRAMJET hypersonic airplane test-flown by NASA last year uses carbon (not carbon fiber, but carbon-carbon) for the leading edge, because it's the only thing strong enough to withstand the heat and stress of flying at 5000mph. Carbon fiber is used in INDY and F1 cars. Built PROPERLY the stuff is strong - and the joints are stronger than the material itself. Any crash that that is violent enough to crack a carbon fame will likely cause extremely serious damage to the rider as well, and you won't care what condition your frame is in. If you like the carbon bike and it's made by a reputable manufacturer just buy it - it'll last longer than you.