Happy Birthday to the United States Marine Corps (USMC)! 234 years!

Recently the Marines announced that they will be blocking social networking sites like Facebook and Twitter.

This seems surprising given that most of the military branches have been supportive of the social networking sites and coming out with official sites of their own.

What are your thoughts? Is this a good idea considering the sensitivity of some of the information being discussed or is it an overreaction on the part of the Marines?