Recently talked to one of their shareholders. Sounds like they're not focused on monetization right now. They're #1 aim is to acquire consumers (millenials preferably), gain scale, and then figure it out. Note that by acquiring millenials they're not gaining share from traditional brokers, they're more likely to expand the pie and get new people to trade. Hopefully these people are quite sticky, and will trade bigger and bigger amounts, by which point they'll be able to offer premium monetization options.

It's a long term play. They're going to be loss-making for a while. Their VC backers can handle it. It's like Transferwise (similar backers) who launched three years ago and who are still loss-making even though they've already processed >$1 billion in transactions...