By changing the expectations for government websites to be that they make all of their content and data available via web services will change the game. Not only are there benefits for the webmasters when they eat their own dogfood, the public can also access, consume, republish, and further disseminate the information in ways that the originating agency hasn't considered and in ways which are more convenient for audiences in the community. The possibilities are extensive and just beginning to make themselves known.
Also, though, this allows an agency to easily create multiple platforms for their content (mobile websites, widgets, alternative interfaces, smartphone apps, and uber-accessible versions). Development is faster, cheaper, and more iterative. At the FCC, we have recently opensourced a Drupal module that makes all of the website content available via API - http://drupal.org/project/contentapi. An upcoming m.fcc.gov is just one example of an easy-to-produce result of this approach, but there will certainly be others to come.