The article was very light on details, so I'd appreciate if could you elaborate on the technical capabilities of the app. I get suspicious when I see comments like:

> One reason that led Y Combinator to invest, Hariharan said, “was the traction with which they hit 2 million users in the U.K., with engagement metrics that almost look like a social network.”

It's a bank app. I can't speak for most people, but I don't open my bank app more than a couple of times a month; it's to pay my CC bill, and to make the occasional bank to bank transfer. If I'm spending a lot of time in the app, I'm probably encountering a problem of some kind.

I also can't link "app engagement" with revenue. Banks make money on mortgages, lines of credit and other financial products. I suppose daily logins allow them to advertise this heavily (my bank does it too, and I hate it), but to draw a line from A to B is a bit of a stretch.