A rogue trader’s losses can get them fired. In the worst instance, they can sink a company. For Zillow, its experience falls somewhere between those extremes. The online property company’s app hooked American users who scrolled through endless home listings. Three years ago it opened a new door, effectively becoming a hedge fund that traded houses. In the quarter that just ended, it purchased nearly 10,000 homes. Unfortunately, it only sold about 3,000. Zillow admitted that it had “unintentionally” overpaid for houses and that it would record a $300m inventory writedown as a consequence.