Ari Levy:

 Ethan Bloch was in junior high school in Baltimore during the dot-com boom.
 For his bar mitzvah — the ceremony that welcomes 13-year-old Jewish boys into adulthood — Bloch received $7,000 in cash.
 It was 1998 and, like so many amateur traders at the time, he plunged his wealth into the stock market, mostly software and telecommunication names like Lucent and Nortel.
 He quickly tripled his money. By age 15, it was all gone.
 “This knocked me over the head and left a burning curiosity that I still carry today,” said Bloch, now 31, from the San Francisco headquarters of his financial-tech start-up Digit. “I realized I didn’t know s— about how any of this was working.”