The problem is that fraud/risk (like tech security) is it often involves black swan events. Everything seems fine right until the point where it's not and you're on the hook for millions of dollars (Stripe is probably in the position where you can afford to take a few black swan type events and survive; a lot of Paypal competitors weren't).
Given that Stripe don't do the "wallet" approach of Paypal and is primarily focused on API customers I'm guessing your risks in general are lower, but I'd recommend you be careful about becoming over-complacent.
Absolutely. Indeed, I'd characterize us as actively paranoid. My point was merely that we're already operating at a scale that needs pretty good fraud systems.
(I think we're mostly in strong agreement.)
I'm one of Stripe's cofounders. For what it's worth -- we already process billions of dollars a year. (More than PayPal when it was acquired.) There'll always be more we can do on the fraud/risk side, but we're already operating at a scale that requires a decent amount of sophistication.