Jim Wilson/The New York Times Laura Arrillaga-Andreessen, with her husband, Marc Andreessen, the Netscape co-founder, says that she was drawn to philanthropy because of her mother’s early death from cancer. By CLAIRE CAIN MILLER Published: December 17, 2011, PALO ALTO, Calif. LAURA ARRILLAGA and Marc Andreessen are practically a royal couple around here. But when they met, on a New …