At twenty-five years old, Anna Wiener was beginning to tire of her assistant job in New York publishing. There was no room to grow, and the voyeuristic thrill of answering someone else's phone had worn thin.

Within a year she had moved to Silicon Valley to take up a job at a data analytics startup in San Francisco. Leaving her business casual skirts and shirts in the wardrobe, she began working in company-branded T-shirts. She had a healthy income for the first time in her ...