David Karp, who founded Tumblr when he was just 21, would deepen his voice on phone calls to be taken more seriously.

Tumblr, the micro-blogging and social-networking site, was founded by David Karp in 2007, when he was only 21. Karp, who worked out of his bedroom in his mother's apartment, admitted he used a deep voice on phone calls and lied about his age when working with other adults.

Karp's lies proved a success, as he is now worth more than $200 million, and he's only 33.