Thinking of Striking it Rich?

Do you know these names?
Sergey Brin (aged 36) & Larry Page (aged 37) of Google each worth US$17.5 billion.
Jeffrey Preston Bezos (aged 46) of Amazon worth US$12.3 billion
Pierre Morad Omidyar (aged 43) of eBay worth US$5.5 Billion (2009)
Mark Zuckerberg (Aged 26) of Facebook worth US$4.0 billion
David Filo (aged 44) of Yahoo worth US$1.4 billion
Jerry Yang (aged 41) of Yahoo worth US$1.3 billion
What do they have in common? Where did they make their money?
How long did they take to make their money? If we are thinking about where to make our pile, where then do you think we ought to look at?

Source of statistics: Wikipedia.