The self-reinforcing loop here has two substantive components. (1) The cost of failure in Japan is pretty high. If your start-up tanks, you are not likely to get funding to try another one, or for that matter to even get a decent salaried job anywhere. (2) If you have a salaried job in a government office or sizable company, it's nearly impossible to lose it unless you quit -- so people don't quit unless they are extremely confident that they can do better elsewhere. So it's not really a cultural aversion to risk taking. Rather, the whole system offers overwhelming incentives for all but the most senior people to shut up and stay in line.

But I would disagree with the idea that large corporations don't want to take risks -- they are pretty much the only serious risk takers in Japan, and they do it on a huge scale, often more readily than large corporations in other developed countries. Think electronics companies committing to huge assembly lines during the height of the financial crisis, Nomura buying half of Lehman, etc. The real problem is that there is not enough game to be had at more granular tiers of the economy, unless you're in the con artist business.