As computers become more powerful, a lot of the functionality which is reserved for the server side gets pushed to the client. The client ends up with more business functionality which helps in faster rendering, faster response. The application server's primary responsibility gets relegated to access control.
The other aspect of technology that's gradually coming to the fore is real-time communication. This enables even more business logic (in terms of access control) to be pushed to the client. Essentially, as game_the0ry mentioned, the server application gets relegated to a thin CRUD layer. And soon, maybe that CRUD layer will also go away, because the client knows excactly what is allowed and what isnt't.
As the world gets more bandwidth, more connectivity, clients become more stateful.
Conversly, this also proves that business rules are really are not that critical for businesses to function, rather it's the data behind them.