What does this tell us? First, it confirms that general aviation is a risky activity. And if the risks are left unmanaged, they are unacceptable. Second, it tells us that in many cases the fatality was predictable. What these pilots saw was subjective and lacked clearly defined parameters, but still, there was something that made them edgy. Even if we can't define what makes us edgy about certain pilots, to paraphrase Justice Potter Stewart's famous quote on another subject, "we know it when we see it."