When Elizabeth Holmes went to court last year to face 11 charges of defrauding investors and patients through her disgraced biotech company Theranos, it looked like Silicon Valley itself was on trial. If the court came down hard on her, it could end the “fake it till you make it” mantra that seeded so many successful tech firms.

Her $9bn (R143bn) valuation was achieved by pitching a product that was alluring in theory but didn’t work in practice (and quite possibly never would)...