All forms of collaboration require some sort of centralized collaboration tool.
In Drupal this can be implemented with "Multi-Sites", "Organic Groups (OG)", and "Domain Access". These solutions all have their strengths and weaknesses.
The main issue however is when to choose "Multi-Sites", "Organic Groups (OG)", or "Domain Access".
First a short overview of the relevant points:
A 5 page Drupal Brochure distribution that was made for a web designer and is/was used by various designers in a multi-site configuration to provide 5 page Drupal enabled brochure websites for their clients.
Provided as a service with maintenance or on their own host with 2nd line support, all the designer had to do is 'design' and if possible theme. Of course Theming services were and are provided.
I just came across some development snapshots made in 2006 on the development of a database driven RV dealership.
Remember this is Drupal 4.74 CCK,Views,Contemplate, one custom module and some tweaking here and there (sometimes with a pipe wrench).
One of the major things was the theme, and because the designer (at that time) had little theming experience (I think not much designers had then, and this was a good one), I did the initial theming.
I think this was one of my first real interactions with the Drupal Community. It was December 2005.
RV Dealership Project built with cck and views on drupal 4.x.
Access at the legacy project portal.
Guesthouse server, website and promotion project.