[ovi256]

The point of controllers would be to glue together front-end protocol (HTTP in case of web apps) code and hide this from back-end (model) code. Models should be written so that they could be reused in a desktop or mobile app for example without issue. A model would know to check auth or authorization, but would not know that the username and password were coming in through HTTP forms. The controller is the thin layer that hides that.

IMO, the controller is not reusable between frontends. A web user controller would need to be rewritten for a mobile app. The view and templates too, of course. Current technology makes it so that this is mostly a non-issue, as webapps (think: Rails, Django) are written in different languages and use different libraries from mobile apps (think: iOS apps, Android). But we must recognize this is an artefact of current technology that could change, and is not an ideal case.

Anyone writing mobile apps in "web" scripting languages ? AFAIK, the iOS app store forbids non-Objective C apps. I could be wrong.