But I think the reason it's so unexpected is that Drupal is simply too cool & cutting edge for the White House .. which we normally associate with stodginess and somnolent formality.
And you know how RADICAL college students can be. Downright revolutionary at times.
It could also be that we associate politicians with being less-than-honest about their true intentions .. while Drupal is open source, and therefore completely transparent. (Imagine how people might feel if Hitler were caught parading around town wearing a scarf knitted by Mother Teresa.)
Dare I mention how the government TAKES your money .. without even a thank-you note, and gives it to people who have much too much already. While Drupal, released under GPL, is better than free (as in 'free beer'), cuz it's also open source (free as in 'freedom').