> I must admit to being somewhat uncomfortable that Stripe seems to be spreading themselves out into areas outside their core business
The vast majority of Stripe employees (and there are now more than 1,000) work on our core functionality today. But we see our core business as building tools and infrastructure that help grow the online economy. ("Increase the GDP of the internet.") When we think about that problem, we see that one of the main limits on Stripe's growth is the number of successful startups in the world. If we can cheaply help increase that number, it makes a lot of business sense for us to do so. (And, hopefully, doing so will create a ton of spillover value for others as well.)
As we grow, we have to get good at walking and chewing gum -- just as Google or Amazon have. However, while we go and tackle other problems, our aim is not only to continue to improve our core payments infrastructure, but do deliver improvements at an accelerating rate.