Hacking Your Open Source CMS Is Bad When Its Time to Upgrade
In Seth Gottlieb's blog on content management he discusses The Onion's problems with CMS customizations. The Onion used Drupal 4.7, which worked fine, along with the custom hacks they incorporated into the Open Source CMS. It worked fine, that is, until it was time to upgrade. Then the problems started.
Open Source software is great in that it provides developers with the opportunity to customize aspects of it to suit their needs. The problem arises when you have done so, you are on your own when it comes time to upgrade.
Many of the hacks that organizations create are functions that the CMS' community is likely already working on. Some experts recommend that you stick with what you've got, and wait for an official release which supports those features you're looking for, or work with a CMS such as Django, which was designed to be hacked. Otherwise--hack at your own risk.