crashing hurts, and that extra-long carbon steerer can snap off, causing you to bleed and bruise. smh.

oh, and walking your fancy bike home is more brutal than the physical pain, IMO.
Carbon Fiber is good at tension and compression load resistance, not so good at bend-load resistance....the bending induces shear forces in between the various layers of material, and can cause layer separations. the epoxy resin breaks down between the fibers...
it's an engineering thing.

another thing to consider... some folks just stack spacers on until the stem height desired is reached, then stack more spacers on top of the stem clamp, then put the expander plug in and crank it all down... this can cause the steerer to crack too.
the plug needs to be located inside the stem clamp to strengthen the carbon steerer against expansion cracking.

want to see how little resitance to bending a carbon bike frame has? squeeze the top tube in the middle section... but don't squeeze Too Hard!
that is why everyone gets so concerned about clamping a CF bike in a Workstand....the tubes crush really easily. crushing is a form of bending. Now.. apply heavy torque to a sticking Bottom Bracket with a big wrench... the top tube, in the stand's clamp, BENDS some, in an s-curve.