Market disrupters are having a moment. Disrupters—companies that subvert established business models, often using modern technology—purport to better serve the consumer. In some industries, they make a strong case. You can buy a quality mattress online without being hounded by commission-hungry salespeople. You can hail an affordable ride that arrives in minutes. You can stream a near-infinite collection of music and movies for a flat rate and never pay a late fee.