Imagine, for a moment, that your most clandestine internet searches—anxiety-riddled deep dives on WebMD, Google queries wondering if your cat is trying to kill you, or why farts smell the way they do—were the key to finding a soulmate. Would you sign up for a dating site that guaranteed connection in return for your browser history? For more than a decade, developers have tried to perfect the science of compatibility. Tinder promised infinite swipes. Bumble let women make the first move...