I think Drupal is a great fit in terms of President Barack Obama's desire to reduce cost and to act quickly. Drupal's flexibility and modularity enables organizations to build sites quickly at lower cost than most other systems. In other words, Drupal is a great match for the U.S. government.
Second, this is a clear sign that governments realize that Open Source does not pose additional risks compared to proprietary software, and furthermore, that by moving away from proprietary software, they are not being locked into a particular technology, and that they can benefit from the innovation that is the result of thousands of developers collaborating on Drupal. It takes time to understand these things and to bring this change, so I congratulate the Obama administration for taking such an important leadership role in considering Open Source solutions.
This is a great move for a whole bunch of reasons, and is yet another example to point to when you run into that thankfully increasingly rare type of person who claims open source isn't secure. The "reduce costs and act quickly" bits are important to remember as well.
Once you get on an open platform the possibilities really open up.