[Rails] (resend - sorry!) Which controllers?

[Tony Mobily]

Hello,

I have recently started learning RoR. I think it's _fantastic_. I am  
absolutely blown away.
OK, this is to prepare you to my idiotic question. Hopefully, I won't  
be stoned.

I am designing a simple application, where users can register, and:

* Publish a photo album
* Publish a simple blog with comments
* Determine their list of friends and foes

The application will obviously have a front end and a backend.
The front end will give people a chance to search, and "find" members  
and blogs
The back end will allow people to manage their profiles and add blog  
entries.

Now: I like the idea of urls like this:

domain.com/user/merc/blog

Where:
* "user" is the controller
* "merc" is the user id
* "blog" is the action (in this case, show the blog)

The backend could be:

domain.com/backend/merc/blog

Where everything is as above, a part from the fact that "backend" is  
the controller.

This does mean that each controller will have quite a few actions.

I guess my question is: how do you decide what a "controller" is and  
does? How should I divide the application amongst several controllers?

Well... I hope I didn't embarrass myself too much.

Thanks a lot and bye!

Merc.