According to Philip Rosedale :
"I think the magic of Silicon Valley (and, most visibly, San Francisco) is not in fostering risk-taking, but instead in making it safe to work on risky things. The phenomena is larger than the people: having traveled a lot, I would argue that the entrepreneurs and engineers in San Francisco are pretty much the same sorts of people as the ones you'd find anywhere.
But there are two things happening in Silicon Valley that are qualitatively different from New York or London (or pretty much anywhere else): First, the sheer density of tech entrepreneurs per capita is 10 times greater than the norm for other cities, and second, there is a far greater level of information sharing between entrepreneurs here. Putting a sharper point on that second one: In New York City they ask you to sign NDA's, and in San Francisco we don't. And what may feel a bit risky for the one turns out to have a big positive benefit for the many."