The Department of Defense has allowed the use of social media (like Facebook, Flickr, Delicious, Vimeo and Twitter) on some military networks. This is part of a trend. Last year, bowing to growing pressure from the troops, the U.S. Army unblocked such access for 81 bases in the United States. This came three years after the Department of Defense blocked troop access to YouTube, MySpace, Metacafe, IFilm, StupidVideos, FileCabi, BlackPlanet, Hi5, Pandora, MTV, 1.fm, live365, and Photobucket. Since then, other sites, like Twitter, were added to the blocked list. This meant that anyone using a computer connected to Department of Defense network (NIPRNET), was no longer able to reach the banned sites. No more, at least in most cases.
One reason for the ban was quite practical. All those video and audio clips were jamming up the network, and making it difficult to get official business done. This is a problem university networks began to encounter in the 1990s, and solved by a combination of expanding capacity, and restricting how much students could use the network for downloading large files. The Department of Defense is in a slightly different situation, because many of its users overseas depend on satellites for their Internet connection. Land based fiber-optic lines can provide a lot more capacity, but in combat zones like Iraq and Afghanistan, satellite is often all that's available.
But that satellite access made the Internet available as well, and the troops loved it. Aside from the obvious popularity of email and use of messaging systems, the Internet also provided access to social networking systems (Facebook has nearly 400 million users). These gradually became a popular way for American troops overseas to keep in touch with the folks back home, and with each other. The ease-of-use that has made these sites so popular with civilians, was equally attractive to troops who don't have much time to spend on the Internet. Most troops in Iraq and Afghanistan have access to the Internet, but often via the equivalent of a dial-up connection. So MySpace and Facebook are convenient enough for troops to quickly post messages, pictures and short videos.
The brass were not happy with all this social networking, because of potential security (the enemy obtaining useful data on military operations) problems, but were reluctant to attempt a crackdown. The suspect (of leaking military secrets) troops can be hard to identify, if they want to be, and have proved to be very responsible when it comes to OPSEC (Operational Security, not giving out info that can help the enemy). The brass have also learned that taking away Internet access would cause a serious morale problem.
Twitter has become popular with commanders and technical team leaders, for keeping in touch with their subordinates. Flickr is where everyone keeps their photos. So, for the moment, the military will scrounge up the bandwidth to make some social networking sites available. The new policy still allows local commanders to block access if there are bandwidth (capacity) problems.