Founders: Adam D'Angelo, 26; Charlie Cheever, 29
Year founded: 2009
Location: Palo Alto, California
2010 Revenue: Undisclosed
2011 Projected Revenue: Undisclosed
While working at Facebook in 2009, Adam D'Angelo and Charlie Cheever had a question: Why isn't there a place on the internet where a question can be answered by someone who actually knows the answer?
That question led the pair to start Quora, a Q&A website that allows users to share knowledge. You can pose a question, answer a question, and edit others' answers. The concept wasn't exactly new, but D'Angelo and Cheever knew exactly what would make Quora unique: quality.