It's not Joomla, but Drupal is in the same sort of family/community of CMS and Open Source Software. So, with the White House choosing an Open Source CMS, hopefully, companies that are stuck in the unfounded fear of Security, or worry about not using a Microsoft or Windows system will realize the benefits. More about the US Administration's choice: Open Source Movement Finds Friends at the White House
But Brian... why don't you use Drupal? Isn't it better? Well, 'better' is subjective, as a report last week at CMSwire shows Joomla as the most popular CMS...
The Most Popular Open Source CMS
According to a report issued by CMSWire (registration required), the Joomla! community has created the world's most popular open source content management system.
Remember that Internet Development moves at a very quick pace, and each CMS will get better and better as more and more people participate in the process. The web is about Open Standards (which Microsoft is finally learning), and the more open standards, the better for all involved.
Open Source does not mean Free. It means 'open for all to see and change.' Oops, I said 'change' and I was hoping not too. Oops, I said 'hope'.