About 12 years ago a friend of mine was on a "B" pace ride with other club members. He was riding a relatively new full CF bike, a model that has been used in the pro peloton. It had never been crashed. He was a conservative rider who weighed maybe 170. While slowing down for a red light, not a panic stop, the head tube instantaneously broke free from the top and down tubes, and Jay was over the bars. The impact of his head (yes, helmet in use) on the pavement broke his neck, and he was rendered a ventilator-dependent quadriplegic. He died of complications related to his paralysis a few months after the accident.
Data point of one.