Astro Teller, talking about the culture of failure at Google X:
When the leadership can fail in full view, "then it gives everyone permission to be more like that."
Cultures that allow for failure at the top are (in my experience) extremely rare. Success and age breed risk adversity (cf. this excellent post by Felix Salmon), and leadership positions tend to be filled by successful people.
Willingness to fail is also, in my mind, the single most important factor to long term success. Failure offers lessons which are more learnable - and more causal - than success does. In the absence of failure, one's ability to learn is highly compromised.
To me, willingness to fail should be a top priority to everyone. Discussions of risk should be between all parts of an organization. A company's policy on risk & failure should be explicit, and its implications should be clear to all employees and stakeholders.