There's no question that Wayfair (NYSE: W) has been a success on the stock market. Since its 2014 IPO, the stock has more than tripled, and those gains have come almost entirely since the start of 2017. Revenue growth has accelerated after declining for several previous quarters, and investors now seem convinced the company is here to stay as it approaches $6 billion in revenue this year.However, one big question has loomed over the stock for its entire history: Will Wayfair ever be profitable?