Big marketers have been taking get-to-know-you tours of Silicon Valley for years, with tech companies literally rolling out the red -- or in Yahoo's case, purple -- carpet. They have helped those marketers understand then-new concepts such as online-display advertising, search and social networking. But today, there's less concern with just what kinds of ads marketers can buy and more interest in the product roadmap at spots like Google, Facebook and Hulu -- as well as lesser-known startups.
