SAN FRANCISCO, FEBRUARY 20: When it comes to the marketing craze among Web-based start-ups, the most powerful advertising executives aren't in the advertising business at all. They are the people of Sand Hill Road, Silicon Valley's venture-capitalist enclave.That venture capitalists find themselves immersed in marketing says a lot about the evolution of the business of Silicon Valley. For years, venture capital here underwrote the development of technologically advanced products to be used by - and marketed to - a highly specialized group of customers. Now, just about anyone with a Web site and a product or service to sell on that site can qualify as a high-tech entrepreneur worthy of venture-capital financing.
