On one sun-baked July morning in Silicon Valley Palantir’s lean 45-year-old chief executive, with a top-heavy mop of frazzled hair, hikes the grassy hills around Stanford University’s massive satellite antennae known as the Dish, a favorite meditative pastime. But his solitude is disturbed somewhat by “Mike,” an ex-Marine–silent, 6 foot 1, 270 pounds of mostly pectoral muscle–who trails him everywhere he goes. Even on the suburban streets of Palo Alto, steps from Palantir’s headquarters, the bodyguard lingers a few feet behind.

“It puts a massive cramp on your life,” Karp complains, his expression hidden behind large black sunglasses. “There’s nothing worse for reducing your ability to flirt with someone.”