Does a Start-up Need to Be Based in Silicon Valley to be Successful?

Does a start-up have the best chance to succeed if based in Silicon Valley?  Or would the same start-up be just as successful, if not more successful, if it were based somewhere else?  This firm has developed a large client base supporting start-ups and tech-focused small businesses outside of Silicon Valley, so we have personal experience in working with young companies which have thrived both from inside the Bay Area as well as outside the Bay Area.  The firm has also seen companies fail in both places.  While location is not necessarily indicative of success or failure, it can definitely be a contributing factor.  There is a perception in the start-up world that technology-focused companies in particular should be in Silicon Valley, and as a result, young companies of all sizes do struggle with the question of whether or not their business should be based in Silicon Valley.  What factors might a company look at to make a decision?    I think this start-up founder, who has just moved his business from San Francisco to San Diego has a unique perspective to share on this subject:

Why I Moved My Startup From San Francisco to San Diego