At a $159B valuation, how does Stripe determine what they should build vs. buy? John Collison (@collision): “I remember asking Aaron @levie of Box how product prioritization should work. He was like, ‘Make a big list of all the product things you want to do, & then do the things that'll be most impactful.’” “And you're like, ‘Thanks. Sounds very actionable.’” “But it's a little bit like that on the build vs. buy. You should buy the companies where you're better off buying them than building…