From ars technica:

The United States Air Force has stirred up controversy with a new Internet filtering policy that aims to prevent Air Force personnel from reading blogs while on the job. The ban has been implemented by the Air Force Network Operations Center (AFNOC), which houses the Air Force Cyber Command. The block is said to extend to virtually every web site that contains the word "blog" in the address, but doesn't impede access to sites that are deemed by AFNOC to be "reputable media outlet[s]".