What's the colour of their money?
Jack Dorsey, Twitter chairman and co-founder
Love it or loathe it, Twitter has become a contemporary phenomenon, with users including US President Barack Obama. A stock market flotation is much anticipated and would value the firm at well over $1bn (€0.72bn).
Michael Birch Bebo founder
The founder of social networking site Bebo, which drew its audience primarily from a younger demographic, was initially a huge success. So much so that AOL forked out $850m (€610m) for it in 2008, making Birch a fortune. AOL sold the business this year for less than $10m (€7m). Not so good.
Niklas Zennstrom Skype co-founder
In 2005, Ebay bought Skype for $2.6bn (€1.9bn) in cash and stock, making an estimated $300m (€215m) for Zennstrom. Last year it sold a 65pc stake in it for $1.9bn (€1.4bn) to private equity and venture capitalists.
Chad Hurley YouTube co-founder and CEO
Sold to Google in 2006 for $1.6bn (€1.2bn) in stock, the deal made him a multimillionaire.
Divyank Turakhia Directi co-founder and CEO
Famously turned a $600 (€431) loan from his parents into a company that's worth more than $300m (€215m).