In reply to Andreas Nurbo.

To me the only distinction that needs to be made is that WordPress is *an* application platform, not "the" application platform for every kind of application. In other words, there are some cases where WP fits well. think that's the only distinction that needs to be made.

Using WP as a backend is really attractive for certain things, allowing you to write all the UI/view layers with your own (say, clientside) frameworks. The nice thing is you can self host the backend, i.e. put it on your own choice of hosting or on your own hardware. You don't get the same liberties with hosted backend services.