The US Department of Defense issued a memo last week that states it intended to begin blocking network access -- including that of soldiers serving overseas -- to several popular "Internet entertainment sites" from yesterday.

The 12 sites to be blocked, according to a story in the Associated Press, include several large social networking and media sharing sites like MySpace, YouTube, MTV, Pandora, and Photobucket.

Earlier this month, the US Army cracked down on soldiers' personal blogs, citing security concerns. Operational security, according to the memo from the DoD that was cited in Monday's AP article, is also a reason behind the new ban on MySpace, YouTube, and other social media sites. But that's not all -- "recreational traffic," the memo said, is a drain on bandwidth.

DoD network operations, the memo said, "(have) noted a significant increase in use of DoD network resources tied up by individuals visiting certain recreational Internet sites".

However, according to the AP article, some critics of the policy said that social media sites were an importantant way of keeping in touch with families and friends as well as a news source.

"This is as much an information war as it is bombs and bullets," Wired defense blogger Noah Shachtman is quoted as saying. "And they are muzzling their best voices."