<...> 
>  Static websites don't require an ORM, and don't use business objects.
>  So ActiveRecord would be pretty much useless.

Some static sites are dynamic but with slow dinamics :). For these it is very
convenient to have content in DB and have administration interface
written in Rails.
Because content doesn't change so often (or for security reasons) such
site then can
be crawled to static pages which are put on public web server.

When the need for really dynamic site will come this way will make
transition very easy.

<...> 
>  At best, it would be awkward: adding a directory 5 level deep, which
>  is quite common for a static website, would entail creating a 5 level
>  controller namespace - awkward and rarely done in Rails.
<...> 

This is not true. Not everything in the routes must be a controller.

>  One could easily imagine a
>  static-website management tool integrating a much better - or at least
>  more suitable - templating solution than ERB.

I guess I either have a problem with my imagination or my needs
are so simple that ERB and some helpers suit them very well...


Regards,
Rimantas
--
http://rimantas.com/