This is the killer moat. It's hard enough to build a competent app for 2 app stores and make any money, that developers have no time/energy to build for a third

This is the killer moat. It's hard enough to build a competent app for 2 app stores and make any money, that developers have no time/energy to build for a third one. Microsoft screwed up badly while they still had the chance by changing paradigms rapidly. They (correctly) tried to pay developers to build apps for them, since you don't really need a million apps, you just need the top 30 to work. The problem was that Google owns many of these top 30 and they weren't interested in helping Microsoft obviously. You can't have a winning mobile platform without YouTube, Maps, and for many, Photos/Gmail/Translate.