Thanks for all the replies. I am just researching all of this for my own startup and it is important to understand all the tradeoffs. And it is clear from your article that AWS has a very deep feature set. Its a good article!
Actually, technically, StackExchange is not profitable yet: (http://www.joelonsoftware.com/items/2015/01/20.html). However, "We could just slow down our insane hiring pace and get profitable right now, but it would mean foregoing some of the investments that let us help more developers."