Update: I wrote this Econ paper in 2007 while I was still in college. At that time, I didn't even have installed Drupal. Thanks for the comments!
The market of CMSes has become hotter since the web 2.0 movement. Drupal and Joomla the top 2 open source CMSes are consolidating in the market. This consolidation could be beneficial to software giants Microsoft and Google; therefore Microsoft and Google could secretly finance Drupal and Joomla.