28. MICHELLE ZATLYN
$980 million SOURCE: Cybersecurity AGE: 42 • RESIDENCE: San Francisco SELF-MADE SCORE: Zatlyn cofounded web infrastructure and security company Cloudflare in 2009 and helped take it public a decade later. Today, the firm says it blocks 70 billion cyberthreats a day for more than 4 million customers. With the stock near record highs, Zatlyn, who owns 5% of the company, briefly became a billionaire in early July.