The barrier was the _distribution_. Before the app store, you'd have to make a website of some sort to sell your app. And then you'd have to advertise your app,

The barrier was the _distribution_. Before the app store, you'd have to make a website of some sort to sell your app. And then you'd have to advertise your app, and so on. The app store does all that for you, so that you just build your app and that's it.