From Carahsoft:
Managing the vast quantities of information government entities need has become incredibly challenging. When the Freedom of Information Act was enacted in 1966, no one considered the vast quantity of information that would need to be accessed or the complexity of keeping private data private, while making public data accessible.
Legacy content management systems weren’t designed to manage information with these demands. Not to mention integration with other key systems. This is where open standards based solutions like Alfresco and Drupal provide value.