Back in 2007 I announced and launched a service to host Drupal 5 sites. The underlying technology relied on database views and triggers from MySQL 5. It was a total mess.

Fast forward to 2010. When I recently checked on the new features in Drupal 7, I suddenly realized that it might be possible to create Drupal sites interactively on a master site, in a similar fashion to the 2007 approach, but without the mucking about with Drupal guts.