I don't think it's so bad if you have a clean server side API that enforces your business rules. The application code can then be run anywhere. I assume you'd

I don't think it's so bad if you have a clean server side API that enforces your business rules. The application code can then be run anywhere. I assume you'd write code for client side execution (i.e. don't fetch unneeded data, reduce round trips) and get the the server side excecution and a battle tested public API for free. This seems similar to the approach Parse is promoting with their service.