The NYT reports that the Army has started moving its field guides, traditionally written by theorists and strategists, to a Mediawiki site. The goal is to get more real-field examples and experience from active soldiers and consolidate the vast collection of printed field guides into a single source.
With the Army following in the footsteps of the Department of Homeland Security and the State Department, its clear that the Government has seen the wiki light in a big way. An article on usa.gov talks about how wikis can be used in government and lists several successful examples.