An idea for breaking through Silicon Valley's social network. It can be viewed as a generalization of Hacker News.
You can think of Hacker News as an example of this idea since it allows unknowns to contact PG -- particularly if their submission is voted up to the front page.
More generally, what about using a social news site specifically built for this purpose (and not just for contacting the people who created the site)?
The idea is that if many people agree that you have something interesting to say to someone famous, then he/she would probably be interested in hearing what you have to say.
Moreover, a famous person is more likely to respond to a question if he/she feels the response would be of interest to many people.