By David Randall NEW YORK (Reuters) – When the nine-person startup he co-founded was bought by Facebook for a reported $15 million in January, Cemre Gungor, 27, was inundated with phone calls and emails from wealth advisers. Yet he spurned them all, opting instead to open an account with Betterment, an online financial adviser launched in 2010 that automatically invests in a portfolio of exchange traded funds based mainly on a clients age. My personality doesnt lend itself to being the sort of person who would research good wealth managers and then trust them with making decisions. I dont want to spend any time thinking or caring about that, said Gungor, who grew up in Turkey and Finland before moving to the U.S. He and others of his generation are posing a challenge for wealth advisers who are streaming into Silicon Valley and San Francisco after the public stock offerings of companies such as Facebook, LinkedIn and Twitter helped California create more millionaires than any other U.S. state since 2009.