America's 10 Fastest Growing Private Companies

(From Left) Valentino Volonghi, Peter Krivkovich, Aaron Bell, Adam Berke Courtesy Company
5 of 11


Aaron Bell, CEO and Founder
San Francisco

No. 7
2011 Revenue: $12.4 million
Three-Year Growth: 11,082%

Aaron Bell was writing commercial software at 12 years old and worked at Microsoft before graduating from Stanford. But in 2007, he made the curious decision to switch from computer engineering to advertising. Quoting Mad Men’s Don Draper, Bell says, "Kids don’t grow up wanting to be in advertising," but he was drawn to the space because of it's challenging technical problems. Bell created an advertising platform that offers targeted web advertising for companies worldwide. AdRoll’s clients include Armani Exchange and TiVo, and AdRoll customer Scottevest reported a more than 3:1 ROI on money spent on the service. In July, the company completed a $15 million funding round.