Personally, I separate my projects and tasks between 'private' and 'business'. Currently I use tags and name my projects 'P: fix kitchen sink' or 'W: finalize marketing plan' to separate these areas . But that is somewhat annoying, because tags are not part of the main navigation.
And I don't want my private projects to be listed in the same as area as my business projects, because if I open Doit in my browser and want to show my colleagues something, they don't need to see that I have to fix the kitchen sink.
It would therefore be AWESOME, if you could add tabs for 'All Areas', 'Area 1', 'Area 2', 'Area 3' etc. to
- Focus
- Projects
- Goals
- Contexts
- Filters
The Goals feature could be used for this, if enhanced a bit. It already allows you to group projects etc in exactly the way you are referring to, but it lacks the associated features necessary for being able to actually use them for anything meaningful.