Written by François Zaninotto wrote:
When faced with the alternative between an off-the-shelf CMS or a custom development, many companies pick solutions like ezPublish or Drupal. In addition to being free, these CMS seem to fulfill all possible requirements. But while choosing an open-source solution is a great idea, going for a full-featured CMS may prove more expensive than designing and developing your own Custom Management System.
Given number of available open-source CMS solutions, building one on your own sounds like a stupid idea. But if your website is 50% content management and 50% something else, you probably need to start with a web application framework like Symfony or Django, rather than a CMS. These frameworks provide plugins that do part of the Content Management job already, so creating a CMS today is like assembling Lego bricks to build something that exactly fits your needs.
Federico Cargnelutti 
why not add Zend Framework to the list?
I couldn’t agree most!
Yhe most popular CMS’s are built with so many features
and versions suport, that a simple
alteration is likely to detonate
an atomic bomb!
I recentely developed a common CMS; full-featured,
secure but simple!
And the development has progressed considerably.