Defense Department networks are no longer a BlackBerry-only zone according to Stars and Stripes.
Only Dell devices running Dell's version of Android 2.2 are approved and, to make matters even more restrictive, Dell has discontinued their Streak tablet line running Android, but their Venue smart phones remain on sale.
Classified information cannot be accessed on the devices and browsing must be performed through a DoD proxy server. Users cannot access the Google Android market (and certainly not 3rd party markets).
Click here for the PDF memo from the DISA (Defense Information Systems Agency) announcing the Security Technical Implementation Guide (STIG) for Android. Click here for the actual STIG.
The DISA has efforts underway at an earlier stage to support Apple's iOS and Windows Phone, but Android's open source design is probably better suited to their needs, as it is easier to audit both the hardware and software. DoD could make a custom Android distribution on their own and direct the production of Android models with OEM manufacturers in order to audit the hardware designs.
Still, as this Bloomberg report explains, various US military operations are developing mobile apps both for Android and iOS. Previously, the only approved devices were RIM BlackBerries.
Hat tip to Slashdot.