Founders: Drew Houston, 28; Arash Ferdowsi, 25
Year founded: 2007
Location: San Francisco
2010 Revenue: Undisclosed
2011 Projected Revenue: Undisclosed
At a Boston bus station in early 2007, Drew Houston opened his laptop to finish some work while waiting for his bus. As he turned on his computer, he froze. "I could see my USB drive sitting on my desk at home, which meant I couldn't work," the now 28-year-old says. "I sulked for 15 minutes and then, like any self-respecting engineer, I started writing some code. I had no idea what it would eventually become."