avoiding carbon on the used market is not an absolute... but sage advice as you may not be able to determine thru routine inspection if there is damage to the integrity of the frame... I would say it is more of a guideline for ebay where you often cannot inspect prior to taking possession... you just have to be exceptionally careful when buying used carbon... some guys will go as far as saying NEVER and other will say only if I can get a structural analysis done via MRI/xray/etc...