26t%3D1425937047000%26v963D2%26pos ition%3D5%26china_variant%3DFalse&utm_medium=10today.0309&position=58/part=s1&china_variant=False> nytimes.com / STEVE LOHR Jeffrey Hammerbacher is a number cruncher — a Harvard math major who went from a job as a Wall Street quant to a key role at Facebook to a founder of a ... read more <h