BobbyMods

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:

"Multi-Sites"

• separate (sub-)domains
• can use one or multiple databases