Hiring here is usually done based on specific skills. A person's ability to fit into a corporate culture is far less important. To be sure, there is a culture at most companies, but the three-month product life cycle takes precedence. The Valley hires mainly from those already in the Valley or from recent college graduates. In many cases, a Ph.D. is preferred.
Many employees job hop between projects.
The average employment period with any one company is two to three years and shrinking. It seems that a product's life cycle is the determining factor. Startups and the gamble of immense riches excite the entrepreneur. However, once they have gone through half a dozen startups over the course of a few years, even the risk-takers may want more stability in their lives. They then evolve into the second class of individual.