I'm having a hard time figuring out the right use case for Content Management Systems. At first glance, everything is about content, so why don't we build everything in Drupal/WordPress/Joomla, etc., and bolt more things on top? But then, there are specialized tasks that some applications perform (chatting, file storage, etc.) that are best done the custom way and then optimized.
When do CMSs make sense? When do they not? Will it be a good idea to build a Basecamp clone in a CMS?
I'm looking forward to a fruitful discussion on this.