Logan Green and John Zimmer, 34, 34
Zimmer was warned he wasleaving a “sure thing” when he quit Lehman Brothers to help Green with a carpooling website called Zimride. Months later, Lehman collapsed, but Zimride morphed into Lyft, making the duo two of the most successful entrepreneurs of the past decade. This year, the No. 2 ride-hailing service behind Uber has surged, benefiting from its arch rival’s troubles: Over the past year, Lyft’s valuation has doubled to $15 billion, and its U.S. market share jumped from 20% to 35%. Next up? Bike-sharing.
40 Under 40