Controller Organisation

[eluser]pickupman[/eluser]
I've done it both ways. When I first started using CI, I put everything in the Admin controller for all of my admin stuff. Then as you mentioned it became of lot of nested stuff in the code where the methods almost become the controllers. It became a lot easier to maintain the code later, when you can go back in various controllers and update/edit the files. You may also find it help that you could port your code to another application you may write in the future. Suppose you wrote a blog/news controller to generate front end page content, you may able to drop that controller into another app.
Check out this post in regards to controlling front end and back end controllers.