4. Catherine and David Cook

Founders of MyYearbook.com

At the age of 14 and 16, these siblings created a social network because they didn’t like their photos in their school year book. They started MyYearbook.com using a computer in their bedroom. Within 6 years, it acquired more than 25 million users across the U.S. and the duo raised $17 million in financing. This site still attracts 20,000 new accounts each day.

In July 2011, a publicly traded Latino social network, Quepasa, acquired MyYearBook.com for $100 million. On this David Cook said, “I don’t consider this an exit or the end. I consider it the end of the beginning, and I believe we have a lot more innovative products to create.”