>>1214652It depends on the type of steel. Plain ol' CrMo and gaspipe will be more likely to simply bend than break. The air-hardened heat-treated CrMo and stainless are more brittle, and are more likely to snap. Not something that happens often, just like carbon grenading isn't something that happens often.
>>1214644Carbon manufacturing techniques have improved enormously over the past decade, and continue to improve every year. Poorly made carbon frames have a lot of areas with lumps and wrinkles in the fabric and areas with too much resin, particularly around bends, which is where the spontaneous cracks would happen. Improved manufacturing techniques have resulted in much more uniform and smoother construction. There are also techniques that are starting to allow for drilling, multi-directional load-bearing (there are some carbon frames that accept racks and panniers now), S&S couplers, and so on, and good designers can make the frames crash-tolerant, too.
One of the biggest problems that carbon has now is that the frames tend to be way too stiff. Not really a problem for MTB. For road, there are ways around that, like Bianchi's CV tech (which works well) or the suspension systems that Calfee and Pinarello have tried (which really don't), or just by fitting wider tires. For compliance I'd still go with Ti or steel, but good frames built from either of those materials are as expensive as a decent carbon frame, anyway, since expertise is the most expensive part of any build.
