Number 15: Heavy trafficIn the late 1990s, Daniel Lewin, pictured, left, and his MIT faculty adviser, math professor Tom Leighton, pictured, right, devised a model for speeding up the movement of large quantities of data over the Internet. Their work became the foundation for Akamai Technologies Inc., the Cambridge company that today handles up to 30 percent of the worlds Internet traffic. Lewin became a billionaire. But on Sept. 11, 2001, he was on American Airlines Flight 11, which crashed into the north tower of the World Trade Center. He was 31.